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Full text of "Natural history of the ground squirrels of California"

737 
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1918 




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REPRINTED FROM 
Volume VII, Numbers 11-12, Pages 597-708, 

OF THE 

Monthly Bulletin of the State Commission of Horticulture 



NATURAL HISTORY 



OP THE 



GROUND SQUIRRELS 

OF CALIFORNIA ^ 

By JOSEPH GRINNELL and JOSEPH DIXON 



Contribution from the University of CaHfornia 
Museum of Vertebrate Zoology 




REPRINTED FROM 
Volume VII, Numbers 11-12, Pages 597-708, 

OF THE 

Monthly Bulletin of the State Commission of Horticulture 



NATURAL HISTORY 



OP THE 



GROUND SQUIRRELS 



OF CALIFORNIA 



By JOSEPH GRINNELL and JOSEPH DIXON 



Contribution from the University of California 
Museum of Vertebrate Zoology 



CALIFORNIA STATE PRINTING C^ICE 

SACRAMENTO 

19 18 

First iB^ned January Ui, 1910 



*IJS 1 1 J986 






■%\ 



JUL 7 -1949 



'-*'^^ 




CONTENTS. 



Page 

Illustrations 4 

Introduction 5 

Acknowledgments 6 

'Key to the Ground Squirrels of California 8 

California Ground Squirrel 9 

Fisher Ground Squirrel 44 

Catalina Island Ground Squirrel 49 

Douglas Ground Squirrel 52 

Rock Squirrel 58 

Oregon Ground Squirrel 59 

Belding Ground Squirrel 67 

Stephens Soft-haired Ground Squirrel 73 

Mohave Ground Squirrel ; 75 

Yuma Hound-tailed Ground Squirrel 76 

Death Valley Round-tailed Ground Squirrel 80 

Palm Springs Round-tailed Ground Squirrel 81 

Sierra Golden-mantled Ground Squirrel 83 

Inyo Golden-mantled Ground Squirrel 89 

San Bernardino Golden-mantled Ground Squirrel 92 

Desert Antelope Ground Squirrel 94 

Nelson Antelope Ground Squirrel 103 

Los Banos Antelope Ground Squirrel 110 

Summary of Points of Special Importance from the Standpoint of 

Ground Squirrel Control 112 

Literature Cited 115 



Note. — Fisaires indicating page numbers refer to folios at foot of pages 



ILLUSTRATIONS. 



Plate 1. 
Plate 2. 
Plate 3. 
Plate 4. 
Plate 5. 



Fig. 


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Fis 



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30. 



PLATES. 

Page 

California Ground Squirrels 5 

Douglas Ground Squirrel and Oregon Ground Squirrel 52 

Belding Ground Squirrel and Sierra Golden-mantled Ground Squirrel- _ W 

Yuma Round-tailed Ground Squirrel and Mohave Ground Squirrel 76 

Desert Antelope Ground Squirrel and Fisher Ground Squirrel 98 

figures in text. 

Page 

Ears of several species of ground squirrels 9 

A typical example of the California Ground Squirrel 13 

Four characteristic poses of a California Ground Squirrel 15 

Mound and burrow entrance of a California Ground Squirrel : 16 

"Hog-wallow" land, showing burrow of the California Ground Squirrel_ 18 

Plot of excavated burrow of a male "digger" squirrel 19 

Plot of excavated nesting burrow of a female "digger" squirrel 20 

Plot of excavated coloniel burrow-system of "digger" squirrel 21 

Nest of male "digger" squirrel 23 

Nest of female "digger" squirrel 24 

Nest and small young of "digger" squirrel 25 

Diagram showing extent and height of breeding season in California 

Ground Squirrel 26 

Drawings to show relative extent of cheek-pouches in California and 

Belding Ground Squirrels 33 

Heads of wheat gathered by one "digger" squirrel 35 

Metropolis of "digger" sciuirrels in a grain field ^_ 36 

Badly infested hillside 41 

Map showing distribution of the "digger" squirrels 46 

Map showing distribution of the Oregon, Belding, Stephens Soft-haired 

and the Round-tailed Ground Squirrels — 61 

Plot of excavated nesting burrow of Oregon Ground Squirrel 64 

Life photographs of Oregon, Belding and Sierra Golden-mantled Ground 

Squirrels 69 

Plot of excavated burrow of female Belding Ground Squirrel 71 

Third-grown young Belding Ground Squirrel — 72 

Diagram showing the ranges of California Ground Squirrels according 

to life-zones 78 

Map sliowing distribution of the Golden-mantled and Antelope Ground 

Squirrels 86 

Hibernating San Bernardino Golden-mantled Ground Squirrel 93 

Feet of Desert Antelope, Stephens Soft-haired and California Ground 

Squirrels, to show tubercles and extent of hairing 95 

Young Desert Antelope Ground Squirrel — 101 

Young Nelson Antelope Ground Squirrel 106 

Adult pair of Nelson Antelope Ground Squirrels 107 

Diagram showing relative economic importance of different ground 

squirrels 114 



Note. — Figures indicating page numbers refer to folios at foot of pages. 



NATURAL HISTORY OF THE GROUND 
SQUIRRELS OF CALIFORNIA. 



By JOSEPH GRINNELL and JOSEPH DIXON. 

Contribution from the Museum of Vertebrate Zoology, of the University of 

California. 

INTRODUCTION. 

Human occupancy of a new country always tends to upset the primi- 
tive balance of things. Man either purposefully or incidentally begins 
at once to modify the original complement of animal and plant life both 
through destruction of native species and by bringing in with him alien 
kinds. Some native species become more and more restricted in range, 
even disappearing altogether; others tend to increase and spread, 
finding conditions for their existence to be improved through man's 
activities. 

In the case of the ground squirrels of California, we have a group of 
mammals which seems to have in many places benefited by human 
invasion. This is probably due to the destruction by man of the many 
predatory animals, such as hawks, eagles, coyotes and badgers, which 
under original conditions kept the small herbivorous mammals in check, 
and in part to the improved food supply made available to the ground 
squirrels through his cultivation of crops. Because of the destructive- 
ness of these rodents to the planted crops and native forage upon which 
man is dependent to a large extent directly or indirectly for his own 
food supply, the problem of ground squirrel control has become one 
of very immediate agricultural and pastoral importance. 

It would seem that knowledge, as full as possible, of the ground 
squirrels of California is necessary to determining the most successful 
means of controlling them and to applying these means properly to the 
varying conditions throughout our state. This knowledge should in- 
clude the main distinctions by which each may be known from its 
relatives, the distribution of each of the species, the extent of the bur 
rows, the breeding rate, the food habits, and, indeed, every other class 
of facts obtainable relative to their natural history. It is not often 
apparent, in advance, which facts will and which will not prove of 
critical importance in economic work. 

To illustrate the value of a thorough knowledge of the food habits 
of the animal in question, when the most efiicient method of controlling 
destructive rodents is sought, we need only to point to the present 
method used in poisoning the California Ground Squirrel by the use 
of barley coated with strychnine, rather than barley soaked in a strych- 
nine solution. By applying a knowledge of the food habits of this 
animal it was possible greatly to increase the effectiveness of poisoned 
grain because of the discovery by Stanley E. Piper, of the United States 
Biological Survey, that this squirrel is more readily poisoned through 
the membranous walls of its cheek-pouches when merely carrying the 
poisoned grain than through the stomach after the poisoned grain 
has been eaten. Strychnine-coated barley has not, however, been found 



598 THE MONTHLY BULLETIN. 

SO successful when applied to the Oregon Ground Squirrel, which animal 
apparently does not habitually gather and store seeds and grain to a 
large extent, but is active chiefly during the spring and early summer 
when green vegetation, upon which it depends for food, is to be had. 
Some sort of green baits might be expected to be more effective with 
this species. 

It is very desirable at this time that we know more about the extent 
of Eestivation and hibernation among our ground squirrels. "We know 
little or nothing of the effect of gases upon squirrels in this condition; 
and it is obvious that such part of a squirrel population as is dormant 
at the time of a poison campaign will escape destruction and become 
a nucleus of reinfestation. 

During the past spring and summer our work of excavating squirrel 
burrows after the occupants had been gassed, has shown that one fre- 
quent cause of failure in the ordinary waste-ball method of applying 
carbon bisulphid is due to the fact that sudden elevation in the course 
of the burrow, of as much as two feet in some cases, prevents the heavy 
gas from reaching the animal. This condition was found to occur 
much more frequently than is generally supposed. 

The instances just cited all suggest that the present knowledge of 
our ground squirrels is far from complete, and they serve to emphasize 
the above contention that a more thorough knowledge of this subject 
is essential to securing the most intelligent and efficient methods of 
control of these our chief rodent pests. It is the purpose of the present 
paper to supply the information available from all sources in as much 
detail as it has proven feasible for the authors to secure it at this time. 
The facts and inferences are given just as they came, irrespective of 
whether or not they show obvious and immediate economic bearing. 
They are here available to everyone who is concerned with methods of 
control. 



ACKNOWLEDGMENTS. 

The present paper has been prepared at the suggestion of Mr. Gr. H. 
Hecke, California State Commissioner of Horticulture, and Mr. W. C. 
Jacobsen, Superintendent of Rodent Control under this commission. 
Both these men have rendered many valuable helps during the progress 
of our work and have co-operated to facilitate its final publication. 
Their emphasis all along has been upon the need of a summary of the 
facts relative to rodent natural history at this particular time, when 
efforts from every direction are being concentrated upon the problem of 
increased crop production. 

Upon the facilities and auspices of the Museum of Vertebrate Zoology 
of the University of California the writers have been dependent for 
the opportunity of carrying through their undertaking ; and behind this 
has been the continual financial and moral support of the founder and 
constant patron of the Museum, Miss Annie M. Alexander. The col- 
lections of specimens and the field records contained in this Museum, 
gathered during the past ten years, have been absolutely indispensable 



THE GROUND SQUIRRELS OF CALIFORNIA. 599 



to the present accomplisliment. A total of 1263 study skins of ground 
squirrels taken within this state have been examined in the course of 
our work. 

In the spring and summer of 1911, two field assistants from the 
United States Public Health and Marine-Hospital Service were assigned 
by Dr. Eupert Blue, then Surgeon in Command, San Francisco, to 
accompany the Museum party working in south-central California, for 
the purpose of increasing the common knowledge of the distribution 
and manner of occurrence of the rodents of the region. Acknowledg- 
ment is here made for the use of certain facts from the manuscript 
report of that year's work made to Dr. Blue by the Director of the 
Museum. 

During the past year, Dr. W. C. Billings, Surgeon, in temporary 
charge, United States Public Health Service, San Francisco, has very 
greatly aided us in having his field men send us specimens of ground 
squirrels, both alive and dead, for experimentation and study. 

To Professor Harvey M. Hall, of the University of California, we 
are indebted for identifying numerous seeds obtained from the cheek- 
pouches of ground squirrels. 

Through special provision of the State Commissioner of Horticulture 
we have been fortunate in being able to have the accompanying five 
colored plates of ground squirrels drawn by the eminent animal artist, 
Mr. Louis Agassiz Fuertes. We thank Mr. Fuertes for the special 
pains he has taken in executing these drawings. 

Color terms used in our descriptions are taken from Ridgway's 
Color Standards and Color Nomenclature (1912). 

Information used by us from published sources is credited through 
the system of author, year and page references to the list of ' ' Literature 
Cited" which appears at the end of this paper. The authority for 
important information obtained from field notebooks or from letters is 
given in parenthesis together with the abbreviation for the word 
manuscript— "MS." 

Joseph Grinnell. 
Joseph Dixon. 

September 13, 1918. 



\ 



600 THE MONTHLY BULLETIN. 

KEY TO THE GROUND SQUIRRELS OF CALIFORNIA. 



Size large: body alone more than 9 inches (228 mm.) long; tail more than 6 inches 

(152 mm.), not counting hairs; ears tall and rather pointed; tail bushy. 
2. A blackish brown wedge-shaped patch on middle of back between shoulders 

Douglas Ground Squirrel (p. 52). 

2'. No blackish patch on back. 

3. Tail longer: without hairs, about 8 inches (203 mm.); no sharply defined 

triangular whitish patch on each shoulder Rock Squirrel (p. 58). 

3'. Tail shorter: without hairs, Ih inches (190 mm.) or less; a more or less 
sharply defined triangular whitish patch on each shoulder. 
4. Size larger: body alone more than 10| inches (273 mm.) long; general 

tone of coloration darker Catalina Island Ground Squirrel (p. 49). 

4'. Size smaller: body alone less than 101 inches (273 mm.); general tone 
of coloration lighter. 
5. Coloration pale in general tone, near light cinnamon-drab; shoulder 

patches clear silvery white and more extensive 

Fisher Ground Squirrel (p. 44). 

5'. Coloration somewhat darker, near wood brown; shoulder patches 

duller white and less extensive California Ground Squirrel (p. 9). 

Size medium or small: body alone less than 9 inches (228 mm.); tail less than 
6 inches (152 mm.), not bushy; ears low and rounded, or else reduced to mere 
rims. 
6. Body with conspicuous lengthwise stripes; coloration varied. 

7. One white stripe on each side of body; under side of tail conspicuously 
white; head not more or less yellowish or coppery. 
8. Smaller: body alone 6 inches (152 mm.) or less; general coloration 

grayish drab Desert Antelope Ground Squirrel (p. 94). 

8'. Larger: body alone 6 J inches (158 mm.) or more; general coloration light 
clay color. 
9. Size slightly greater; tone of color slightly darker, more deeply clay 

color Nelson Antelope Ground Squirrel (p. 103). 

9'. Size slightly less; tone of color slightly paler, more buffy 

Los Banos Antelope Ground Squirrel (p. 110). 

7'. Three stripes on each side of body, one white and two black; head more or 
less yellowish or coppery. 
10. Tail longer: without hairs, about 3J inches (89 mm.). 

11. Tone of coloration lighter; middle of back more of an ashy brown 

Inyo Golden-mantled Ground Squirrel (p. 89). 

11'. Tone of coloration darker; middle of back more of a cinnamon- 
brown Sierra Golden-mantled Ground Squirrel (p. 83). 

10'. Tail shorter: without hairs, about 3| inches (79 mm.) 

San Bernardino Golden-mantled Ground Squirrel (p. 92). 

6'. Body without any stripes: general coloration nearly or quite uniform. 
12. Size larger: body alone more than 7 inches (178 mm.). 

13. Larger: body about 85 inches (216 mm.); middle of back not bright 

reddish-brown, but grayish-brown — Oregon Ground Squirrel (p. 59). 
13'. Smaller: body about 7i inches (198 mm.); middle of back bright 

reddish-brown Belding Ground Squirrel (p. 67). 

12'. Size smaller: body alone less than 7 inches (178 mm.). 

14. Tail round and relatively long: over 3 inches (76 mm.). 

15. Tone of coloration paler, light pinkish-cinnamon 

Yuma Round-tailed Ground Squirrel (p. 76). 

15'. Tone of coloration darker, wood brown 

Death Valley Round-tailed Ground Squirrel (p. 80). 

15". Tone of coloration medium, grayish-brown or avellaneous 

Palm Springs Round-tailed Ground Squirrel (p. 81). 

14'. Tail flat-haired and relatively short: under 3 inches (76 mm.). 

16, Under side of tail pinkish-buff; rim of ear distinct though low 

Stephens Soft-haired Ground Squirrel (p. 73). 

16'. Under side of tail white; rim of ear scarcely discernible above 
general surface of head Mohave Ground Squirrel (p. 75). 



Note. — Figures indicating page numbers refer to folios at foot of pages. 



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I 



THE GROUND SQUIRRELS OF CALIFORNIA, 

CALIFORNIA GROUND SQUIRREL. 
Citellus beecheyi beecheyi (Richardson) 



601 



PLATE I. 



Other names. — Digger Squirrel, part; Beechey Ground Squirrel; Beechey's Mar- 
mot ; Beechey Spermophile ; SpermopMhis ieecheyi, part ; Arctomys beecheyi; Spermo- 
philus grammiirus leecheyi, part; Citellus variegatus leecheyi; Citellus grammiirus 
beecheyi; Otospermophilus beeclieyi. 

Field characters. — A large ground-dwelling squirrel, with long bushy tail, good- 
sized ears, and general brownish coloration ; dull whitish area on side of neck and 
shoulder, and fine dappled pattern of coloration on back and sides, to be seen in close 
view. Length of body alone about lOi inches, with tail (without hairs) about 6J 
inches more. 

Description. — Adults in summer pelage : Top of head, stripe down middle of hind 
neck, whole back, sides, and rump, of a general wood brown tone of coloration, but 
variegated in fine pattern on back, rump and sides by mottlings of snuff brown and 
buffy white ; these mottlings usually line up in transverse rows, the rows being most 
distinct across the rump ; a large area centering on side of neck and involving 




e f g h 

Fig. 1. Ears of ground squirrels to show characters of size and shape in different 
species, a, California Ground Squirrel ; b, Fisher Ground Squirrel ; c, Oregon 
Ground Squirrel ; d, Stephens Soft-haired Ground Squirrel ; e, Mohave Ground Squir- ' 
rel ; /, Yuma Round-tailed Ground Squirrel ; g. Sierra Golden-mantled Ground Squir- 
rel ; h. Desert Antelope Ground Squirrel. All natural size and drawn direct from 
specimens. Note : a and b are extreme examples ; the average difference existing 
between the California and the Fisher ground squirrels is much less; individuals of 
each race can be found which will overlap some individuals of the other in size 
and shape. 

shoulder, and a faint stripe backward a short distance from upper margin of this 
area, dull white. Cheeks dirty white, changing to wood brown color between eye and 
ear ; eyelids white ; whiskers black. Ears tall and conspicuous, finely haired ; color 
of ear inside, pale pinkish buff ; back of ear, front half, black, becoming dull cinnamon 
buff at base and on hinder margin ; fine black hairs extending above rim at tip of 
ear sometimes so numerous and long as to form a small tuft ; whole lower surface 
of body, inner sides of fore and hind legs, and upper sides of feet, pinkish buff ; hairs 
of breast and belly gray at base, this resulting in a darker tone on this area. Palms 
of fore feet naked ; soles of hind feet thinly haired behind tubercles, or else wholly 
naked, due apparently to wearing away of the hairs altogether ; claws brownish black, 
horn-color toward tips. Tail bushy, though not nearly so much so as in the tree 
squirrels, flat haired, parallel-sided, and square or round ended ; hairs along sides of tail 
about 41 mm. (If inches) long, at end of tail the same ; general color of tail both 
above and below buffy grizzled gray, in other words mixed black and buffy white in 



602 THE MONTHLY BULLETIN. 

fine pattern ; the buif tone is deeper below than above ; close inspection shows the 
hairing of the tail to be concentrically banded, three black bands and four light ones, 
the outermost black band being broadest, and the outermost light one constituting a 
peripheral whitish fringe. 

Color variations.- — As far as we can see, the two sexes are identical in coloration, 
save as caused by the greater rate of wear to which the pelage of the female is 
subject during the season when the young are being reared. Wear progresses in some 
cases until most of the colored ends of the hairs are gone, and a dingy light brown 
color is acquired, including also the tail. Molting begins anteriorly and progresses 
backward. 

The material we have studied seems to show but one decided molt in adults each 
year, and this takes place during July and August. Young, however, seem to undergo 
two molts in the first six months of their lives. When one-third grown their pelage 
is characterized by a fluffy texture and a yellowish tone of color, but the general 
pattern is closely similar to that of adults ; when nearly full grown the young are 
smooth-coated and show rather brighter tones of brown and clearer white shoulder 
patches that even fresh-pelaged adults. 

There are not infrequent special, or "sport" variations, in the Beechey Ground 
Squirrel, such as albinos, either complete or partial, which have been reported from 
time to time. We have been told of "black" ground squirrels ; and there is in the 
Museum of Vertebrate Zoology an adult male, from Stanislaus County, taken by 
W. C. Jacobsen, January 30, 1918, which is of a curious light pinkish-buff tone of 
coloration, save for the outermost concentric black band on the tail and for the 
whitish shoulder patches and a suggestion of dappling on the back. 

The color description given above was taken from specimens from the vicinity of 
San Francisco Bay. Specimens from other parts of the general range of the 
Beechey Ground Squirrel depart fi"om this slightly in different respects. Two speci- 
mens at hand from Marysville Buttes, Sutter County, are of paler, grayer tone of 
general color. A series of skins from the western slope of the central Sierra Nevada 
averages whiter underneath and darker brown on middle of back. Examples from the 
southern San Joaquin Valley are paler in tone of coloration and exhibit whiter 
shoulder patches, thus evidently constituting intergrades towards the Fisher Ground 
Squirrel. A series from the coast district of southern- California, from Santa 
Barbara to San Diego, shows darker brown back, but whiter under surface of body, 
and the white shoulder patches are more conspicuously contrasted. Some San 
Diego County examples in rather worn pelage show a curious reddish tinge on the 
rump. 

Measurements.^ — Average and extreme measurements, in millimeters, of twenty 
full-grown specimens from west-central California are as follows : Ten males : total 
length, 435 (405-475) ; tail vertebrae, 164 (150^-175) ; hind foot, 57 (52-60) ; ear 
from crown, 20.5 (17-24) ; greatest length of skull, 59.1 (56.9-61.1) ; zygomatic 
breadth, 36.9 (35.0-39.2) ; interorbital width, 14.1 (13.3-15.0). Ten females: total 
length, 423 (400^-460) ; tail vertebrae, 162 (150-175) ; hind foot, 57 (55-58) ; ear 
from crown, 18.4 (16-20) ; greatest length of skull, 56.2 (53.8-59.5) ; zygomatic 
breadth, 35.8 (-34.3-37.6) ; interorbital width, 13.9 (13.0-14.7). 

It will be seen from the above figures that females are decidedly smaller bodied than 
males though in tail length they are about the same. The skulls of the oldest individ- 
uals, particularly males, show greatest general size, greatest zygomat'c breadth (as 

^The measurements given throughout the present paper have been taken according 
to the following methods. The external dimensions are those recorded on the label 
attached to the skin and were taken from the freshly killed animal by the collector 
in each case. Total length is the distance from the tip of the nose to the tip of the 
last vertebra of the tail (which is also practically the tip of the tail without the 
hairs), the body and tail being straightened out but not stretched; tail vertehrw is 
the length of the tail alone (again without hairs), from a point on upper side at base 
where tail can be bent at right angles to back, to tip of last vertebra ; Mnd foot is 
measured when extended flat at right angles to leg, from heel to tip of longest claw ; 
ear from crown is the distance vertically from top of head at inner base of ear to 
extreme tip of ear, not including hairs. The cranial measurements were all taken by 
the senior author, with parallel calipers reading to tenths of millimeters, from 
cleaned skulls. Greatest length of skull is taken parallel to axis of skull from ante- 
rior tips of nasals to most posterior point or points on skull (this in some skulls falls 
on the condyles, in some on the lambdoidal ridge) ; spgomatic width is the greatest 
width of skull at right angles to axis, from the outer surface of one zygomatic arch 
to the outer surface of the other ; interorbital width is the least distance between the 
eye-sockets, but not counting the little notch usually present in ground squirrels on 
each edge of the interorbital portion of the roof of the skull. 

10 



THE GROUND SQUIRRELS OP CALIFORNIA. 603 

compared with total length of skull), broadest jugals, stoutest postorbital processes, 
highest developed sagittal crest, most nearly approaching parietal ridges (these meet- 
ing also farthest forward), and broadest frontal region (which also shows a concave 
or "dished" upper surface). In otlier words, old animals have skulls which are more 
massive and angular than those of young ones. We find that relative age of an 
individual can be recognized approximately by the relative degree of development of 
the above characters. Amount of wear on the crowns of the molariform teeth and of 
advance in coalescence of the contiguous bones along certain sutures also give criteria- 
for determination of age. 

Weights. — -Average and extreme weights, in grams, of twenty full-grown speci- 
mens from west-central California are as follows: Ten males, 696 (600-923) ; ten 
females, 592 (491-774). Averages in ounces: males, about 24 (1^ pounds); 
females, about 20 (IJ pounds). 

It appears that males are 17 per cent heavier than females. The heaviest speci- 
men out of a total of 36 weighed, was an old male tipping the scales at 923 grams, 
or 32| ounces, or a trifle over two pounds. This animal was shot June 12, 1918, in a 
slaughter yard at Mendota, and was exceedingly fat. 

Type locality. — "Neighborhood of San Francisco and Monterey" (Richardson, 
1829, p. 170). 

Distribution area. — The greater part of central and southern California west of 
the desert divides. Altitudinally, ranges from sea-level up regularly to about 6,000 
feet, and local'y and sparsely to as high as 8,200 feet (in Yosemite National Park). 
As regards life-zone, the California Ground Squirrel is most abundant in the Upper 
Sonoran zone, less so in the Lower Sonoran and Transition, and but relatively 
rare and local in Canadian (see fig. 23). 

More in detail, this squirrel is limited to the northward in the coast belt abruptly 
at the south sides of the Golden Gate, San Francisco Bay, Carquinez Strait, and 
Suisun Bay. Its range extends northward over the eastern half of the Sacramento 
Valley to the Marysville Buttes and its limits thence swing northeastwardly through 
the Feather River country to the southern border of Lassen County. From this last 
point south it covers both slopes of the Sierras nearly to the Yosemite region, but 
thence south to Tulare County, only the western slope. In the vicinity of Lake 
Tahoe it gets a little way into the state of Nevada. To the southward it covers 
most of the San Joaquin Valley, and the coast belt south throughout the San Diegan 
district to the Mexican border, and beyond this even to the San Pedro Martir 
mountains. 

Along the eastern border of its range, from Tulare County south to Riverside 
County, the race beecheyi grades into the race fisheri. The dotted line on the map 
(fig. 17) marks approximately the center of the area of intergradation between the 
two races. As will be seen, the limits of heeclieyi swing west across the southern 
San Joaquin Valley and thence around south so as to exclude the Bakersfield region 
and the Tehachapi, Tejon, San Bernardino and San Jacinto mountains. 

Specimens examined. — A total of 149 specimens from the following localities in 
California : San Francisco County : Ingleside Race-track, 1. Alameda County : 
vicinity of Berkeley, 9. Contra Costa County : Walnut Creek, 12 ; west side Mount 
Diablo, 2. San Mateo County : Sierra Morena, 1 ; Pescadero Creek, 1. Santa 
Clara County: Palo Alto, 1. San Benito County: Cook, 2. Monterey County: 
Monterey, 6. Sutter County : Marysville Buttes, 2. Stanislaus County : Claribell 
Station, 1. San Joaquin County : eight miles southwest of Tracy, 1. Sierra 
County : near Sierraville, 1. Placer County : Dutch Flat, 1 ; Blue Canyon, 1 ; 
Cisco, 2. El Dorado County : Fallen Leaf Lake, 1 ; Kyburz Station, 2. Tuolumne 
County : Aspen Valley, 6,400 ft, 1. Mariposa County : Merced Grove, 1 ; Crane 
Flat, 6,300 ft., 1; Indian Creek, 6,100 ft, 1; Yosemite Valley, 3; Merced Lake, 
7,500 ft, 2; Mono Meadow, 7,300 ft., 1; Chinquapin, 6,200 ft., 1; El Portal, 
2,000 ft, 2; Coulterville, 2; Pleasant Valley, 1. Merced County: Snelling, 1 ; Los 
Banos, 1. Madera County : Raymond, 2. Fresno County : Mendota, 4 ; Panoche 
Creek, at 502 ft., 1 ; Friant, 1 ; Kings River, 5,000 ft., 2. Ventura County : Matilija, 
4 ; Ventura, 3. Los Angeles County : vicinity of Pasadena, 7 ; near Azusa, 2. San 
Bernardino County : near Colton, 4. Riverside County : Thomas Mountain, 6,800 ft, 
1. San Diego County : Warner Pass, 3 ; Grapevine Spring, 1 ; Witch Creek, 8 ; 
Julian, 8 ; Cuyamaca Mountains, 4 ; San Diego, 2 ; Point Loma, 10 ; Chula Vista, 3 ; 
near mouth Tiajuana River, 1 ; Dulzui-a, 7 ; Campo, 1 ; Jacumba, 1 ; Mounta'n 
Spring, 4. 



604 THE MONTHLY BULLETIN. 

The California Ground Squirrel is probably known by sight to more 
people than any other one of our four hundred kinds of native mam- 
mals. It inhabits open ground in well-settled territory and it forages 
abroad during the daylight hours when its movements are most likely 
to attract attention. Numbers are to be seen from the windows of 
passing trains, and the traveller by automobile is often thrilled by the 
narrow escapes of those heedless individuals which dash across the 
road immediately in advance of him, not infrequently to their own 
undoing. Then, too, this squirrel has, perhaps, been more widely 
advertised than any of our other mammals. A few years ago it came 
into prominence as a proven disseminator of the dreaded bubonic plague, 
and it has become notorious for its exceeding destructiveness to culti- 
vated crops. 

The term "Digger Squirrel" is often applied to this species, more espe- 
cially in the foothill and mountain regions, in recognition of its burrow- 
ing habits, to distinguish it from the tree-inhabiting gray and red 
squirrels. The book name, Beechey Ground Squirrel, much used in 
the literature relating to it, is derived from the accepted scientific 
name Citellus heecheyi. This name, heecheyi, was bestowed upon the 
animal by its original describer (Richardson, 1829, p. 170) "in honour 
of the able and scientific Commander of the Blossom," Captain F. W. 
Beechey. The British ship "Blossom" cruised the Pacific Ocean north- 
ward even to Bering Strait during the years 1825 to 1828. Collections 
of specimens were brought back from many localities visited, including 
San Francisco and Monterey; among these specimens was one or more 
of the squirrels in question. These were evidently preserved for the 
most part by Mr. Collie, surgeon of the ship, who is quoted by Richard- 
son as stating that "this kind of Spermophile 'burrows in great num- 
bers in the sandy declivities and dry plains in the neighbourhood of 
San Francisco and Monterey, in California, close to the houses. They 
frequently stand up on their hind legs when looking round about them. 
In running, they carry the tail generally straight out, but when passing 
over any little inequality, it is raised, as if to prevent it being soiled. 
In rainy weather, and when the fields are wet and dirty, they come 
out but little above ground.' " And further information is given, 
according, for the most part, with what anyone can see for himself 
today in the same general region. This attests to the acuteness of 
observation of Mr. Collie, and also shows how the squirrels had already, 
some ninety years ago, begun to impress people with their numbers and 
boldness. 

The California Ground Squirrel may be distinguished from other 
members of the squirrel family by the combination in it of the fallowing 
characters : essentially ground-dwelling habits, relatively large size, long 
bushy tail, tall pointed ears, and generally grayish coloration with a 
three-cornered silvery white patch on each shoulder. Close inspection 
discloses a finely dappled pattern of coloration (see Fig. 2) such as is 
not shown in any tree squirrel or in any of our other ground squirrels 
except its near relatives, the Douglas, Fisher, Rock and Catalina Island 
squirrels. The detailed descriptions, measurements, etc., as given in 
the accompanying small-type paragraphs, should be studied for further 
particulars in this connection. 

12 



THE GROUND SQUIRRELS OP CALIFORNIA. 



605 




IS 



606 THE MONTHLY BULLETIN. 

The species now under discussion is restricted in its distribution 
mainly to the state of California. It extends a little ways south into 
Lower California; and to the eastward it barely crosses the Nevada 
line in the vicinity of Lake Tahoe. To the northward in the coast 
belt it is cut off sharply by the Golden Gate and San Francisco Bay, 
but in the interior it extends to the headwaters of the Feather River. 
Southeastwardly toward the deserts the race heecheyi blends into the 
race fisheri, which in turn is wholly cut off by the hottest deserts 
beyond. (See map, fig. 17.) In the coast belt north of San Fran- 
cisco Bay and from the upper Sacramento Valley northward the 
Beechey Squirrel is replaced by the Douglas Ground Squirrel. 

Altitudinally the California Ground Squirrel ranges from sea level, 
as on the shores of Monterey Bay, up to an altitude of at least 8200 
feet, as in the Yosemite National Park. It is most abundant on the 
plains of the San Joaquin and in the Coast Ranges and Sierra foot- 
hills. As regards life-zone, the metropolis of the species lies in the 
Lower and Upper Sonoran (see fig. 23). It is less numerous in the 
yellow pine belt (Transition zone), and is but rarely or sparingly 
represented in the Canadian zone, still higher on the mountains^ 
Its preferences as to local conditions are not closely limited, except 
that it avoids dense chaparral and thick woods. It frequents pasture 
lands, grain fields, orchards, sparsely tree-covered slopes, small moun- 
tain meadows, rock outcrops on the tops of ridges, and even granite 
talus slopes. It is always most abundant, however, in the open situa- 
tions, and its decided preferences are such that it thickly populates 
much of the best farming and grazing lands in the state, to the great 
reduction of their producing value from the human standpoint. 

This squirrel secures shelter for itself and young, and safety from 
its enemies, by burrowing in the ground. Where possible it chooses 
to excavate its retreats in hillsides or in low earth banks. Here some 
at least of the necessary digging can be done in a horizontal direction. 
But, of course, those members of the species which live on the plains 
or on small flats or meadows in the foothills or mountains must dig 
down vertically for considerable distances to gain the requisite pro- 
tection. Many of the squirrels which live in the granite country 
make their homes under large boulders or in rock taluses where a 
minimum of burrowing is necessary to insure safe retreats. On wooded 
hillsides special safety from enemies that dig is secured by location 
of the burrows under tree-roots or old stumps. 

In the foothill region at the southern end of the San Joaquin Valley 
there seems to be a decided tendency on the part of the ground squirrel 
to select alluvial fans for home sites. This preference may be accounted 
for by the fact that the plants upon which the squirrel feeds make a 
better growth in the deep alluvial soil there than they do on the adjoin- 
ing hillsides which are often steep and with but shallow cover of soil. 
For the same reason the alluvial fans afford easier digging to consider- 
able depth and hence better protection. In seven burrows in different 
localities, in which the squirrels were gassed and then dug out (J. 
Dixon, MS), the extent, diameter and depth were found to vary and to 
depend largely upon the nature of the soil. In shallow adobe or clayey 
soil, underlaid by broken rock, the burrows were found to be short, of 

14 



THE GROUND SQUIRRELS OF CALIFORNIA. 



607 





Fig. 3. Four characteristic poses of a California Ground Squirrel. Photographed by 
J. Dixon at Berkeley in August, 1918, 



15 



608 THE MONTHLY BULLETIN. 

small diameter, and not reaching to any considerable depth. Those in 
alluvial or sandy soil were found to be of large diameter, of greater 
extent, and to reach to much greater depths. 

The most conspicuous signs of activity on the part of ground squirrels 
in any locality are the large mounds of earth that have accumulated 
in the course of excavating the burrows. This earth is commonly 
thrown out in a fan-shaped pile directly in front of, and to the sides of, 
the main entrance to the burrow (see fig. 4). These mounds of earth 
are often three or four feet in diameter and from six to ten inches 
above the general level. They vary greatly in size, but average larger 
in sandy soil than in clayey or rocky ground. The size of the mound 
is, however, no reliable index to the length or size of the burrow except 
in those cases where the burrow is of a straight or simple pattern. In 



i'*ssrdg= 







:<^^^^. 



r'Wcsk-'.tjfc.jBf.s-t « 



Fig. 4. Mound and burrow entrance of a "digger" squirrel, in sandy ground. 
Mounds of earth such as these are often three or four feet in diameter and rise from 
six to ten inches above the general level. The route taken to the feeding grounds 
being used at this particular time is indicated by the numerous tracks at the left-hand 
side of the entrance. Photographed at Tipton, Tulare Coimty, May 23, 1918. 

colonial or intercommunicating burrows the dirt is not always thrown 
out at those entrances which allow of the shortest possible "haul." 

Most of the work of tunnel excavation is carried on during the spring 
months, as is shown by the mounds of fresh, soft earth accumulated 
at the mouths of the burrows in that season. In the lowlands, where 
there is a large crop of wild oats in the springtime, this newly excavated 
earth supports a ranker growth than the surrounding parts of the field, 
so that, as one of our party wrote in his field notes, "the plain looks 
like a cemetery overgrown with grass," with these taller stands of oats 
about the squirrel holes suggesting grave mounds. 

To some extent the ground squirrels, like the pocket gophers, thus 
act on wild land as natural cultivators of the soil, and may thus serve 
a useful purpose. On the other hand, their burrows are frequently 
the cause of much destructive erosion on hillsides during heavy rain- 
storms. Numerous small landslides have been noted on steep hillsides 

16 



THE GROUND SQUIRRELS OP CALIFORNIA. 609 

on the campus at Berkeley, that were plainly caused by the presence 
of squirrel burrows which had concentrated and conducted the water 
in narrow channels instead of permitting it to spread out and soak in 
or run off in the natural way. The presence of squirrels along irriga- 
tion canals results in the embankments becoming undermined by their 
burrows, with ensuing disastrous breaks in the canals, especially at 
times of high water. 

Digger Squirrels are firm believers in the daylight saving plan. 
Their activities above ground are restricted to the hours between sunrise 
and sunset. They love the warm sunshine and may often be seen 
sprawled upon the summits of stumps, rocks or other points which 
afford safety as well, basking in the morning or later afternoon sun- 
shine. During spring and summer they come out of their burrows soon 
after sun-up. They are at those seasons most active during the middle 
of the forenoon and again during the late afternoon, but avoid the 
intensest heat of midday. During midwinter those squirrels which do 
not remain underground altogether make their appearance only late in 
the forenoon of bright sunny days. Light and warmth seem to be 
essential to their successful existence aboveground. 

The observer afield often comes upon ground squirrels which are 
some distance from their holes. Such animals usually run, with bodies 
and tails undulating and closely paralleling the ground, to the near 
vicinity of their burrows, where they then post themselves in upright 
position. They can then watch the intruder, yet be in readiness to 
dart down into their holes at an instant's warning. "While thus on 
watch a squirrel is wont to repeat, at regular intervals of from two to 
five seconds, its characteristic ''bark." This note is really a double 
one, and may be indicated by the syllables, clink-sup. The second 
syllable, however, is not audible for any great distance, while the first 
is loud, staccato, and of decided metallic quality, calling to mind the 
sound produced by the blow of a light hammer on an anvil. The im- 
pression is enhanced by the regularity and frequency of its utterance, 
and this will be kept up five minutes at a time. Sometimes, when a 
squirrel is startled, it gives a more prolonged note, clink-sup-sup-sup- 
sup, the last syllables running together as a sort of chuckle. In any 
event, it is the clink which is the metallic syllable, and which one hears a 
long ways, more or less mellowed by distance. 

If closely pressed the squirrels drop down at once into the protection 
of their subterranean retreats. Ordinarily when thus frightened down 
they do not reappear at the surface of the ground for some minutes, 
five to twenty-five minutes in tested cases, as if to give the suspected 
enemy a chance to tire of his waiting and depart. Occasionally, when 
surprised at a distance from its burrow, a squirrel will crouch motion- 
less, it may be almost at the feet of the oi)server, as if to escape detection 
by the "freezing" ruse. Extreme fear also on occasion may be part 
of the basis for this mode of behavior. 

In some respects the California Ground Squirrel is much "wiser" 
than is generally supposed. This has been forcibly impressed upon 
the junior author during his endeavors to secure photographs. Living 
squirrels were then observed at close range in their various activities 
under natural conditions. Several species of chipmunk, as well as the 
Golden-mantled Ground Squirrel and the Nelson Antelope Ground 

2— 43C0T 17 



610 THE MONTHLY BULLETIN. 

Squirrel, encountered under the same circumstances, soon became accus- 
tomed to the camera so that the photographer, himself at some little 
distance, was able to release the shutter when the lens of the camera 
was less than thirty inches from the animal photographed. Compared 
with this, the Digger Squirrels proved exceedingly wary, refusing to 
show more than their heads even though the camera was disguised and 
placed six feet distant. The confidence of the Digger Squirrel could no 
doubt be gained, given sufficient time; but when an approach was 
attempted by the methods that had proven successful with the other 
squirrels the results were nil. It looks as though the reactions of the 
Digger Squirrel had been adjusted to meet that category of enemies 
which lie in wait at jumping distance. 




Fig. 5. TjTJcal "hog-wallow" land showing trail and burrows of the California 
Ground Squirrel. Photographed ten miles north of Fresno, April 10, 1911. 

Ground squirrels traveling to and fro, between their holes and their 
feeding grounds frequently traverse the same courses until regular 
radiating trails 2^ or 3 inches wide are worn through the grass (see 
fig. 5). This is particularly well seen on many hillsides, and on the 
rolling '^ hog-wallow " lands along the eastern side of the San Joaquin 
Valley, where, in the fall, when the grass and weeds are dry, the trails 
show most distinctly. In the spring, when the new growth is just 
appearing, the trails are still conspicuous, as the vegetation is slower 
in starting there than in the adjacent unbeaten tracts. Soon, however, 
the trails are entirely obliterated, save as the animals renew them by 
further use. 

In foraging for seed-pods, grain, or fruits, the ground squirrel does 
not usually eat the food on the spot where it is gathered, but he stuffs 
it into his capacious cheek pouches (see fig. 13) or else, if it is too 
large for this, carries it in his mouth nipped between the incisor teeth. 
He then repairs to some point of vantage such as a rock pile or to the 
mound at the entrance of the burrow. Here he proceeds to hull and 
devour the food at leisure and at the same time is near enough to shelter 
so that he can quickly duck in should an enemy suddenly appear at 

18 



THE GROUND SQUIRRELS OP CALIFORNIA. 



611 



short range. These "husking places" are conspicuously marked by 
the hulls of seeds and by the rinds and pits of cultivated or wild fruits. 
Examination of these "kitchen middens", will sometimes give a pretty 
accurate idea of the character of the squirrels' rations in any locality. 
A great many of the matured seeds, however, are carried directly below 
ground to the permanent storehouse. 

Droppings, or feces, of the Ground Squirrel are to be observed widely 
scattered rather than deposited in piles. They may be found about 
the "husking places" or along the trails or paths which lead from the 
burrow to the feeding grounds. In the burrows they are accumulated 
in special places evidently set aside for the purpose. The feces are 
generally of a cylindrical shape, rounded at the ends, but are quite 
variable in diameter and volume. In April when green food is 
abundant fresh feces are of a greenish hue and are often soft and 
flattened. During the drier portions of the year the droppings are 
covered with a dark brown coating, while the interior is composed of a 
dry mass consisting of hulls of weed seeds and finely chopped and 
shredded vegetable fiber, from 3 to 10 millimeters long. A typical dry 
dropping measured 16 millimeters (f inch) in length, with a diameter 
of 6 millimeters (i inch), and weighed -^q of a gram. 

The California Ground Squirrels do not dwell in thickly populated 
"colonies" of sharply restricted extent, as is the case with the prairie 
dogs of the Middle West. Still there is with our rodent a tendency to 
occupy certain definite tracts in a general territory to the exclusion of 
intervening places and this without obvious reason as regards food 



/-g /i' '6 /a ZO ZZ 2^ 26 Z8 30 




Fig. 6. Plot (plan and elevation) of used burrow of a male "digger" squirrel, as 
excavated by J. Dixon on an alluvial talus in the foothills near San Emigdio, Kern 
County, April 28, 1918. 

Main entrance at a ; refuse sump in old nest-cavity at & ; "blind" exit in thick grass 
at c. Unusual depth of burrow, as shown in profile, was due to thick rock-filled over- 
lying stratum, beneath which the squirrel had found easy digging horizontally after 
having once penetrated the less resistant part of the layer at the edge of the talus. 

Total length of burrow, 34 feet; average diameter, 4i inches ; greatest depth reached, 
5J feet ; volumetric contents of entire burrow, 4t cubic feet. 



612 



THE MONTHLY BULLETIN. 



supply and kind of soil. It would seem that centers of population 
may arise through the historical circumstance of original settlement by 
first-comers. This would be particularly the case in fields newly 
invaded, where descendants would establish their burrows in the near 
vicinity of their pioneer parents. 

Digging operations were carried on by us during the breeding season 
of the ground squirrel, in quest of all obtainable facts in regard to their 
habits underground. Three general types of burrows were encountered. 
The male squirrels were usually found in short, shallow, simple burrows 
at the outskirts of the "colony." The burrow belonging to a male 
herewith illustrated (fig. 6) proved to be longer than usual with males, 




Fig. 7. Plot (plan and elevation) of used nesting burrow of a female "digger" 
squirrel, as excavated by J. Dixon and G. R. Stewart on a west slope in Strawberry 
Canyon near Berkeley, April 6, 1918. 

Entrance at left; old nest chambers at a; refuse sump at 6; used nest at extreme 
right, which was found to contain the mother and four small young. 

Total length of burrow, 22 feet; average diameter, 4J inches; greatest depth reached, 
30 inches; volumetric content, 41 cubic feet. 

and reached to a greater depth, but its simplicity is characteristic for 
that sex. We failed to secure a single male squirrel in any burrow 
found to be occupied by a female with young. It is believed that at 
least during the breeding season the male squirrels live altogether by 
themselves in their own individual burrows. 

A burrow from which a female and four young with eyes still un- 
opened were secured is shown in fig. 7, It will be seen from this illus- 
tration that the nest burrow of the female is relatively complicated. 
This particular burrow was extremely difficult to follow on account of 
the many turns and ''blind alleys." 



THE GROUND SQUIRRELS OP CALIFORNIA. 



613 



The third type of burrow (see fig. 8) might well be called a "colonial 
burrow," as it is used by both sexes and also by the young after these 
leave the nest burrow and begin to forage for themselves. Colonial 
burrows are used largely as "safety zones." They afford convenient 
places for the squirrels to duck into when danger unexpectedly appears. 
These burroAvs are often from 100 to 200 feet in length and form a 
communicating system of underground runways connecting from six to 
twenty entrances or surface openings. The nests in the colonial bur- 
rows were old and had the appearance of having been used by many 



Z 4 6 6 ro 



4Z 44 46 48 Jo 




Fig. 8. Plot (plan and elevation) of a "colonial" burrow-system of "digger" squir- 
rel in sandy ground in irrigated section near Bakersfield ; excavated by J. Dixon and 
H. G. White, May 3, 1918. 

Various entrances at h; food store at a; "back-door" exit for emergency purposes at 
b; nest cavities as indicated. 

Total length, 138 feet; average diameter, 4| inches; greatest depth i-eached, 4 feet; 
volumetric content, 17i cubic feet. 



individuals at various times. These colonial burrows were not found 
to be in any case used as breeding burrows. It is possible that they 
may have consisted of one-time breeding burrows, now connected or 
linked together. 

The relative extent of any one burrow system is thus dependent not 
only upon kind of ground — in other words, upon the difficulties encoun- 
tered in digging — but ^Iso upon the estate of the individual or indi- 
viduals directly concerned. Table I gives data in regard to the three 
types of burrows. In the seven burrows which were dug out and of 
which careful record was kept, the shortest occupied burrow was five 
feet long and the longest 138 feet. The average was 35.2 feet. The 
average diameter varied from 3^ to 5 inches, with a mean of 4.3 inches. 
The cubic air content was found to vary from 1.03 to 17.8 cubic feet, 
the average being 5.2 cubic feet. 



614 



THE MONTHLY BULLETIN. 



Table I. Data relative to burrows of the California Ground Squirrel. 



Type of 
burrow 


Locality 


Date (1918) 


Lengtli of 
burrow 
(In feet) 


Greatest 

depth of 

burrow 

(in inches) 


Average 
diameter 
of burrow 
(In inches) 


Cubic 

content 

of burrow 

(in cubic 

feet) 


Male 

Male 

Male 

Male 

Female 

Male 

Oolonial 


Strawberry Canyon, Berkeley- 
Strawberry Canyon, Berkeley.. 
Strawberry Canyon, Berkeley.. 

12 miles west of Fresno 

Strawberry Canyon, Berkeley.. 
San Emigdio Creek, Kern Co... 
12 miles south, 5 miles west of 
Bakersfleld 


April 3 
April 4 
April 4 
Blay 27-2S 
April 6 
April 27-28 

May 3 


5 IS 
8 30 
14 30 
26 45 
22 -SO 
34 65 

138 48 


3| 1.03 

4 1.40 
il 2.40 

5 4.6 
il 4.8 
4i 4.8 

i% 17.8 




Average 






35.2 38.1 


4.3 


5.2 















In illustration of the fact of variability in depth and extent of burrow 
system with nature of soil, some actual instances as revealed, by exca- 
vation may be described. The layers of alkali hardpan in the Fresno 
region were found to have a very decided influence on the course of the 
burrows. In most cases where the hardpan was near the surface, the 
burrows were found to extend through the hardpan to the soft ground 
that is often to be found just beneath. No evidence was found to indi- 
cate that the squirrel had dug through even thin layers of solid hardpan 
except at points where natural cracks or openings through it occurred. 
Slight cracks in the hardpan were sometimes enlarged, this apparently 
having been done during wet weather, to sufficient size to enable the 
squirrel, but not such an enemy of the squirrel as a coyote or badger, 
to readily pass through. In following the various cracks and openings 
through and between the strata of hardpan, the burrows were found 
to twist about in very erratic fashion. The sudden elevation in a 
burrow of sometimes as much as two feet was found to form a very effec- 
tive barrier to the flow of any gas such as that of carbon bisulphid, 
which is heavier than air; such a gas would gather into the low places 
(see Stewart and Burd, 1918). 

The deepest burrow system uncovered was situated in an alluvial 
talus in the foothills near San Emigdio, Kern County. The mainte- 
nance of the great depth (from four to five and a half feet for a distance 
of twenty feet) was clearly due to the squirrel having followed a soft 
layer at the margin of the talus down to below the level of the four-foot 
rock-filled surface layer. Beneath this the squirrel had progressed easily 
through the soft soil as long as he kept beneath the rocks — which he was 
practically forced to do (see fig. 6). 

There seems to be little or no evidence to support the rather wide- 
spread notion that ground squirrels burrow down until they reach 
water. A colony burrow was unearthed in an irrigated section near 
Bakersfleld, where the water level was known to be only five or six feet 
below the surface of the ground. No part of the burrow (see fig. 8) 
was found to extend deeper than four feet and hence not down to the 
water level. While ground squirrels do not absolutely require water, 
where surface water is to be had they often go consi(ierable distances 
to secure it, going across the country sometimes as far as a quarter of a 
mile. In many places squirrels are found thriving where it is known 
that it is over 100 feet to ground water and miles to surface water. 



THE GROUND SQUIRRELS OP CALIFORNIA. 



615 



It is quite likely that California Ground Squirrels construct new 
burrows from time to time, or, what is more probable, that each young 
individual as it approaches maturity leaves the parent burrow and 
digs a home for itself. In any event, in places there are many more 
burrows than individual squirrels present at any one time. Some of 
these tunnels, especially in the plains and foothill country, are joined 
together below ground to a greater or less degree and constitute the 
colonial burrows already described. When hurriedly seeking safety 
a squirrel will pitch down into the nearest one of a number of holes in 
the vicinity of the one about which it was first seen. The commonly 
uninhabited burrows may thus serve in extremity as temporary refuges. 

The burrows of the squirrels are often inhabited by species of animals 
other than the rightful owners. Ground owls habitually make their 
homes in squirrel holes, probably deserted ones; and, to a less extent. 



1^ 




ft'Jea.ifeci^-^-'^c 



Fig. 9. Nest and male of "digger" squii-rel as dug out after burrow was treated 
with cartaon-bisulphid. Tlie splierical shape of the nest-cavity and the structure of 
the nest itself is well shown. 



the holes are frequented by California toads, Western gopher snakes 
and Pacific rattlesnakes. It is unlikely that the presence of the latter 
two animals is congenial to the squirrels, as both of these snakes are 
known to eat ground squirrels in numbers. Eegularly communal occu- 
pants of squirrel burrows are scorpions, centipedes and mole crickets. 
Mole crickets were found to serve as reliable indicators of the efficiency 
of the gas when squirrels were fumigated in their burrows. If the 
gas had not killed the crickets it was found that the squirrels had not 
succumbed. 

California Ground Squirrels are accustomed to furnish their under- 
ground quarters comfortably. Special nests are constructed and main- 
tained in good order, where the individual may sleep or rest in warmth, 
free from contact with the damp earth. Each burrow occupied by 
a single squirrel was found to contain at least one well-made nest. In 
some eases there were two, one obviously older than the other. In the 



616 



THE MONTHLY BULLETIN. 



colonial burrow that was dug out, three nests were found, of which two 
were new. The nests were always placed well back in the burrows 
(see figs. 6, 7), where they would have maximum protection from dig- 
ging enemies such as coyotes and badgers. The cavities in which the 
nests were placed were short globular chambers and were usually sit- 
uated slightly above and to one side of the main run, so that the 
drainage was away from rather than into the nest. The cavity in 
which a nest containing a fem,ale and four small young was found 
measured 10 inches in length, 9 inches wide and 7 inches high. The 
nest cavity used by a male squirrel was 12 x 10 x 7 inches (in the same 
dimensional order), while the two nest cavities in the colonial burrow 
measured 12 x 10 x 8 and 12 x 12 x 7 inches, respectively. 

All of the nests found were of similar composition and construction. 
Finely shredded dry grass blades and roots, and fine stems of foxtail 
and needlegrass, formed the bulk of the constituent material. The 
nests were spherical in shape and deeply cupped. The walls were from 




FIG. 10. Nest and female of "digger" squirrel as uncovered after the burrow had 
been gassed. Excavated on the University of California Campus, Berkeley, April 
6, 1918. 



two to two and one-half inches thick. The walls of the nest which 
contained the young squirrels were arched over and met at the top, 
forming a sort of a canopy. Entrance to this nest was gained through 
a hole near the top. The material in the walls had been compressed 
or felted into a thick, warm fabric. The outside dimensions of this 
nest were 10 x 9 x 7 inches, while the inside cavity measured 6x4x5 
inches. Compared with that of the female just described, the nests of 
male squirrels were smaller, had lower walls and were more loosely 
constructed (see fig. 9). The nests of the males did not completely fill 
the cavities in which they were placed, as did the nest of the female. 
A nest occupied by a male measured 8 x 10 x 7 inches outside and 
4x5x4 inches inside. The three nests in a colony burrow excavated 



THE GROUND SQUIRRELS OF CALIFORNIA. 



617 



were large and evidently of considerable age, since the foxtail blades 
and stems composing the nests were old and broken up into short bits. 
One of these nests measured 12 x 10 x 8 inches outside and 6x5x4 
inches inside, while the other measured 12 x 12 x 7 inches outside and 
6x4x5 inches inside. The third nest was old, being merely a flat mat 
of trampled down bits of foxtail stems. 

The nest of the female (fig. 10) was 30 inches below the surface of 
the ground. The nest of a male was 28 inches below the surface, while 
the two used nests in the colony burrow were 20 and 24 inches under- 
ground. The female and the male nests were in clay ground and the 
two colonial in sandy soil. The average depth of nests below the sur- 
face of the ground, taking into account all of the nests found, was 30 
inches. 

Contrary to general belief, we have found ground squirrels to be 
very cleanly animals about their nests and burrows. No feces (drop- 
pings or dung) were found in any nest. Such material was found 




Fig. 11. Nest and small young of "digger" squirrel after removal of the female. 
Same nest as shown in Fig. 10. 

heaped up in piles in special chambers usually just off the main run, but 
within easy reach, 18 to 24 inches, from the nest. These sumps were 
lower than the nests and were sometimes nothing but old nest cavities 
which had been dug somewhat deeper than they had formerly been. 
In the burrow of a male squirrel, a pile six inches in diameter and 
two inches high, of feces soggy with urine was found in a sump slightly 
below and fourteen inches distant from the nest. Female squirrels 
appear to be more particular in this regard than the males, in that the 
sump is farther removed from the nest. 

The nest that contained the four young squirrels (see fig. 11) was 
alive with fleas, which swarmed over the helpless young. These fleas 
persisted in remaining in the nest for three days after the young 

25 



THE MONTHLY BULLETIN. 



squirrels had been removed. Other nests were found to be infested 
with fleas, though at least one-half of the nests examined were free from 
these parasites. In certain localities squirrels were taken that were 
to casual appearance absolutely free from fleas, while in other localities 
squirrels taken were invariably infested to a greater or less extent. 
The species of flea that infests ground squirrels is not the species that 
commonly attacks human beings. While ground squirrels are their 
preferred hosts, we found that the former did not object to human 
society when their squirrel hosts had died. At least two methods are 
used ijy the squirrels to rid themselves of these uninvited guests. The 
first, or dust-bath method, is that of suffocation of the fleas which hide 
in their fur by thorough wallowing in especially dusty places. The 
second is by digging a new burrow and making a new nest, thereby 
leaving the bulk of the fleas behind. 

Some years ago it was discovered that the fleas harbored by the 
California Ground Squirrel carried the bacillus of bubonic plague. A 
vigorous campaign of extermination was waged against the squirrels 
by the United States Public Health Service and they were practically 
eliminated from many areas, locally, in the San Francisco Bay region. 



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Fig. 12. Diagram showing extent and height of breeding season in the California 
Ground Squirrel. Heavy line shows percentage of females pregnant, for weekly periods 
from January to May. Based on record of embryos found in over 10,000 females 
examined by the United States Public Health Service (McCoy, 1912, p. 1070). 

Soon after the efforts against the squirrels were relapsed the latter 
began to ''spill in" from adjacent areas until now in places they are as 
numerous as ever. Nevertheless the prime object was attained, that of 
eliminating the foci of dissemination of the disease. 

It is extremely important to know definitely the season and rate of 
breeding of any economically important, rodent. Fortunately for our 
purpose, there is available for the California Ground Squirrel abundant 
data, supplied through the records of the United States Public Health 
Service (see McCoy, 1912, p. 1070). As will be seen from the accom- 
panying diagram (fig. 12) based on over 10,000 females examined, the 
iDreeding season is restricted to a comparatively brief period of the 
year. Pregnant female ground squirrels have been taken in the Bay 
region as early as the first week in January, but the main breeding 
season does not begin until February, and it is practically concluded 
by the middle of April. The largest per cent of pregnant females is to 
be found during the last week in February. By June 4 only two-tenths 
of one per cent (0.2) of females examined contained embryos. At higher 



THE GROUND SQUIRRELS OF CALIFORNIA. 619 

altitudes, where warm weather comes on much later and more abruptly, 
these breeding dates would be correspondingly later and the breeding 
season still more restricted. 

While males and females occur in practically equal numbers, mating 
seems to be promiscuous; there is no permanent pairing off. 

The number of young per litter, as ascertained from counts of 
embryos, varies from 4 to 11. The average, from very extensive records 
kept by the United States Public Health Service (McCoy, 1912, p. 
1070), may be inferred to be very close to 7.2. The same records serve 
further to show that there is some variation in size of litter from 
month to month. The average for February is 6.9 ; for March, 7.3 ; 
for April, 7.5 ; for May, 6.8. The tendency seems to be toward slightly 
larger litters in April, which is beyond the date of maximum number 
of pregnant females (see fig. 12). Number of mamma3 (nipples), 
which is usually six pairs in this species, occasionally but five, is no 
criterion for number of young per litter. All the evidence at hand 
indicates that each female raises but one litter each year. A female 
ground squirrel was taken on the University campus at Berkeley, on 
March 13, 1918, which contained eleven embryos each of which meas- 
ured three-fourths of an inch long. Eight of these were contained in 
one branch of the uterus and three in the other. Another female 
taken at the same time contained eight embryos, each of which measured 
five-eighths of an inch long. Five of these were in one branch of the 
uterus and three in the other. 

On April 6, 1918, G. E. Stewart and the junior author dug out two 
female ground squirrels which had been previously gassed in their bur- 
rows. One of these females was found in a nest with four small young 
which we took to be about ten days old, since their eyes were not yet 
open. These baby squirrels averaged 170 millimeters or 6f inches in 
length; a typical one weighed 61 grams, or a little over 2' ounces. 
They were well covered with hair, which already showed on the back 
the characteristic dappled pattern of the adult squirrel. The tail, 
however, was nearly round and showed little sign of the fringe of hairs 
along the sides. Their stomach contents showed no sign of their having 
eaten green vegetation or anything else than milk. Data from other 
sources indicate that the young are not completely weaned until they are 
at least half grown. The other female secured in an adjoining burrow 
not over ten feet distant was found to contain seven small embryos each 
of which measured three-eighths of an inch in length. These embryos 
could not well have reached full development short of two or three 
weeks, so we have a variation of nearly a month in time of birth at one 
locality. 

Cases such as those just given are thought to be exceptional and may 
serve in part to explain the occurrence of late litters such as have been 
the basis of the claim that this animal has two litters a season. Litters 
of young squirrels which sometimes appear very late in the season are, 
too, likely to be merely the result of efforts to replace first litters of 
young which have met an untimely death. Thus two litters might be 
born in one season, though only one raised. 

Shaw (1916, p. 4) gives 24 or 25 days as the period of gestation in 
the Columbian Ground Squirrel (Citellus columhianus) in the region 
about Pullman, Washington. The period of gestation of the California 

27 



620 THE MONTHLY BULLETIN. 

Ground Squirrel has not to our knowledge been determined; yet the 
facts at hand, such as the general rate of development of the embryos, 
and of the young after birth, lead us to believe that it is close to thirty 
days. 

The bulk of the young ground squirrels in any one locality make 
their appearance with remarkable uniformity as to size and regularity 
as to date. Our data is incomplete, as to exact time of birth; but we 
have plenty of records of embryos in various stages of development, 
and we can observe the time of appearance of the young squirrels above 
ground. In the lowlands the majority are probably born the last of 
March, and by the last of April the first born are beginning to appear 
aboveground, playing about the mouths of the burrows. In the higher 
altitudes the young are born later. Females in the Transition Zone 
and lower part of the Canadian Zone had not yet given birth to their 
young in June. '' Spring" in the lowlands comes in April, while the 
spring of the higher altitudes does not occur until late June or July. 
Hence the young do appear at the same season, considering the differ- 
ences in temperature conditions at the different elevations. The 
accumulation of a certain quantity of heat from without seems to be 
necessary each year to start the squirrels breeding. 

Young California Ground Squirrels may be considered fairly preco- 
cious. They ordinarily begin to venture outside their nest burrows 
when yet very small, in ascertained cases only cne-fourth or even one- 
fifth the weight of the adults. They are then probably not over four 
weeks old. At Snelling, Merced County, on May 28, 1915, C. L. Camp 
(MS) observed that young ''evidently just emerging for the first time 
in their lives, seemed confused when they saw a horse and buggy and 
often ran almost directly under the wheels." Two months later, in 
the high mountains, the young squirrels behaved the same way. A 
probably abnormal occurrence was that of a very young squirrel found 
on April 29 wandering aimlessly about in the grass near a burrow 
entrance. This squirrel weighed only 61.5 grams, or less than one- 
tenth the weight of adults. It was practically helpless and would have 
fallen easy prey to any sort of predaceous animal. 

The first litter of young ground squirrels seen aboveground in the 
season of 1918 by the junior author was noted on April 28 at 1,500 
feet altitude on San Emigdio Creek, Kern County. In this litter there 
were six young at least one-third grown. Judging from the "sign" 
about the burrow, these youngsters had been foraging above ground for 
a week or ten days. The season at this altitude was at least ten days 
later than it was down on the lower parts of the San Joaquin Valley. 
Several burrows of small diameter and amateurish construction were 
found at the edge of a thick patch of alfilaria that grew near the nest 
burrow. These young squirrels in spite of their small size were busily 
harvesting the heads of the ripening alfilaria and when alarmed ran 
down the small burrows which each had dug for himself. While the 
observer was standing over one of these burrows a youngster came up 
halfway out of a hole six feet away, but catching sight of him gave 
a hasty alarm note and scurried back down the hole. Twenty-five 
minutes elapsed after this before any of the young squirrels reappeared 
above ground. 



THE GROUND SQUIRRELS OP CALIFORNIA. 621 

As far as is to be observed, the male takes no active interest in the 
welfare of the young. Indeed, he dwells altogether separately from the 
family and does not see his offspring until they begin foraging out of 
doors. His only function at all, as regards the upbringing of the 
young, is that of sounding general alarm throughout the colony when 
danger threatens. As for the mother, even she is notably indifferent 
to her young after they appear above ground. When suddenly alarmed, 
she flees to safety on her o^vn account, leaving the youngsters to shift 
each for himself as best he may. 

The rate of growth of the young is such that they reach mature size 
by September, when they are from four to six months old (McCoy, 
1912, p. 1069). But before this time, by the first of August, the young 
of the year begin to emigrate locally, so as to establish each for himself 
a new home. It is likely that this process of emigration is hastened by 
the development on the part of the parents of an attitude of incom- 
patibility. According to this idea the initial solicitude of the mother 
for her young at the helpless age is later reversed, so that she becomes 
antagonistic to them and finally speeds their departure. The young, 
at the same time, begin to give evidence of an instinct to wander. At 
any rate, the month of August sees the important phenomenon of emi- 
gration or dispersion well under way. Young of the year then put in 
their appearance in unexpected places; new ground is invaded, and 
the total territory occupied by the squirrels increased in extent insofar 
as the increase in population makes necessary and the favorable nature 
of the country permits. Undue congestion of population tends thereby 
to be prevented. 

The natural enemies of the California Ground Squirrel are of many 
kinds, and under original conditions so many as regards individuals 
as to provide a regular automatic check to any abnormal increase of 
the squirrel. The most important are golden eagles, red-tailed hawks, 
coyotes, badgers, wildcats, weasels, rattlesnakes and gopher snakes. 
Each of these various animals pursues the squirrels in its own particular 
way. Hawks and eagles swoop down on them from their vantagd points 
in the air. Wildcats and coyotes lie in wait near the burrows until 
the squirrels venture forth in search of food, when they pounce upon 
them. Badgers, weasels and snakes capture the squirrels in their bur- 
rows. Some specific cases will be cited here. It must be remembered 
that, while casualties to squirrels may be inflicted by their customary 
enemies almost hourly in any general neighborhood where man has not 
exterminated these predators, the chances of a person's being in a 
position at the critical moment to witness a tragedy of this sort are rare. 
At the San Emigdio Eanch in Kern County on April 25, 1918, the 
junior author watched a Golden Eagle (Aquila chrysaetos) capture and 
devour an adult ground squirrel. The eagle was first observed flying 
quietly down a canyon. By weaving in and out in its course the bird 
was able to skirt the irregular hillside so as to keep within fifteen or 
twenty feet of the ground. At length the eagle skimmed abruptly 
around the shoulder of a hill, just clearing the tops of the wild oats, 
and dropped quickly dowu upon a luckless ground squirrel. The latter 
had evidently been on a foraging expedition and did not have time to 
reach his burrow, so complete was the surprise. The eagle seized the 
squirrel with both sets of talons, and the piercing grip by these effective 



622 THE MONTHLY BULLETIN. 

instruments quickly dispatched it. The bird then proceeded to tear 
the animal to pieces with the stout beak and, perched on the ground, 
devoured it on the spot. The strategy and success of this method of 
attack was obviously dependent upon the eagle keeping close to the 
ground so as to remain out of the squirrel's range of vision until the 
last moment. 

At Pleasant Valley, Mariposa County, on May 17, 1915, C. L. Camp 
(MS) fed a ground squirrel that had been shot, to a Golden Eagle kept 
captive by a storekeeper there. The eagle ate head, skin and bones, 
but discarded the stomach and large intestines. Other birds, such as 
the turkey vulture, have been observed by the junior author to similarly 
avoid the stomach and intestines of ground squirrels that have been 
killed by taking poisoned barley. Coyotes have also been known to 
show the same fine discrimination when eating ground squirrels which 
they themselves have not caught. 

Some idea of the success with which Golden Eagles sometimes pursue 
ground squirrels may be had from the fact that at Lilac, San Diego 
County, on April 4, 1907, James B. Dixon (MS) found eleven freshly 
caught ground squirrels in and about an eagle's nest that contained 
two eaglets about a week old. 

During the spring of 1904 W. L. Finley and H. T. Bohlman observed 
and photographed a pair of young Golden Eagles in various stages of 
development from the time the eaglets were nine days old until they 
left their birthplace nearly three months later. The aerie was a bulky 
affair placed in a horizontal fork of the upper limbs of a large sycamore 
tree that grew in a canyon back of Mission San Jose, Alameda County. 
In speaking of the food of the Golden Eagle, Finley (1906, pp. 9-10) 
says: "His food consists almost entirely of the ground squirrels that 
are so abundant through the California hills. On our second trip [on 
April 12], when we looked into the nest, we found the remains of the 
bodies of four squirrels lying on its rim. At each visit we examined 
the food remains and the pellets about the nest, and we are sure that 
a very large proportion of the eagles' food supply consisted of squirrels. 
... I am satisfied that this family of eagles regularly consumed an 
average of six ground squirrels a day during the period of nesting, 
and, very likely, more than that. . . . But even this low estimate would 
mean the destruction of 540 squirrels along the hillsides in about three 
months' time." 

The nest of a Western Red-tailed Hawk (Buteo horealis calurus) 
examined by J. B. Dixon (J. Dixon, 1917, p. 12) on March 28, 1906, 
and containing one day-old chick, two pipped eggs and a rotten egg, 
was found to contain also the remains of two ground squirrels. This 
was near Vista, San Diego County. At Pala, in the same county, the 
same observer found the nest of a E-ed-bellied Hawk {Buteo Uneatus 
elegans), April 3, 1916, containing three young, a week old, together 
with one ground squirrel and two pocket gophers. The dead squirrels 
counted in the nests represent, of course, merely the surplus which the 
old birds had just carried to the young. The squirrels that the old 
birds themselves or the young may have eaten on the day of observation 
are not taken into account. 

At Dunlap, Fresno County, on September 30, 1916, H. S. Swarth 
(MS) found a large rattlesnake (Crotalus oreganus) which showed a 

30 



THE GROUND SQUIRRELS OP CALIFORNIA. 622 

bulge in the middle portion of its body. This proved to mark the loca- 
tion of a full-grown ground squirrel, which had been swallowed entire, 
head first. 

Near the mouth of Tejon Creek, Kern County, on July 16, 1914, C. L. 
Camp (MS) watched a rattlesnake (Grotalus oreganus) about three 
feet and a half long, swallow a ground squirrel. He describes the 
incident essentially as follows: The snake had just bitten the squirrel 
on the side of the face below the eye. The squirrel flopped about for 
five or ten minutes and then dropped over a bank and died, out of sight 
of the snake. The snake then slowly crawled down over the bank after 
its prey, found it, touched it all over with the end of its tongue, and 
then seized the animal by the nose. The squirrel moved slightly. The 
snake drew back and waited motionless for some time. The snake then 
got a fresh hold on the squirrel's nose, pulled the body out straight, 
and started to work its jaws over the squirrel's head. Things went 
rapidly as far as the squirrel's ears, then operations proceeded more 
slowly. The snake writhed about and gradually worked its jaws over 
the shoulders of the squirrel, first moving the upper jaw forward with 
slight jerks and then pulling up on the lower jaw. Finally, after the 
rodent had been half swallowed, we approached closer to take a picture 
and the snake disgorged the squirrel as the result of a violent effort 
lasting a minute or so. We went away and in a little while the snake 
returned to its food and had swallowed it almost completely within 
15 or 20 minutes more. 

On Pine Flats, in the San Gabriel Mountains, a large, lazy rattler 
was secured which showed a bulge about halfway along its body. Dis- 
section disclosed a full-grown California Ground Squirrel which had 
been swallowed. (Grinnell, J. and H. W., 1907, p. 53.) 

On San Emigdio Creek, Kern County, on the morning of April 23, 
1918, the attention of J. Dixon (MS) was attracted by the nervous 
barking and peculiar actions of a large male ground squirrel. With 
the aid of the binoculars, the actions of the squirrel, which was less than 
75 yards distant, were easily followed. The squirrel was obviously 
much wrought up and his sharp, nervous notes were quite different in 
pitch and intensity from the ordinary metallic alarm note. The ani- 
mal's attention was continually focused upon an opening just beneath 
a certain small white rock at the edge of a stone pile. While his atten- 
tion thus remained fixed, the squirrel kept running back and forth in 
a semicircle about thirty inches distant from the object concerned. 
During this time the squirrel's tail, which was held arched over his 
back, was twitched violently sideways every time he barked. The 
alarm notes were uttered during a momentary pause at the end of 
each advance in the arc-shaped path of the squirrel. The squirrel's 
whole demeanor reminded the observer of that of a pup that has cor- 
nered some old pussy cat and still hesitates to make an attack. Having 
witnessed three similar performances by ground squirrels, in San Diego 
bounty, the observer proceeded to investigate and found, as in the three 
previous instances, that a coiled rattlesnake was the cause of the excite- 
ment. In the present case there were two, a male and female, tightly 
coiled together at the mouth of a squirrel burrow, and they were dis- 
patched. An hour later this same squirrel, which was easily identified 
by a peculiarity in its pelage due to wear, was observed digging a new 



684 THE MONTHLY BULLETIN. 

burrow some fifty feet distant from where the rattlesnakes had been. 
There was no way of determining whether the presence of the snakes 
had influenced this action, but it was evident that this squirrel made 
no effort to fill up the entrance to the burrow which had been pre- 
empted by the snakes. It is a popular notion that ground squirrels, 
when the opportunity offers, bury snakes alive. 

As for mammals as enemies of ground squirrels, the evidence most 
readily obtainable is derived from examination of the excrement of 
the former. Coyotes have regular places for deposit of excrement, on 
hill tops or ridges. Bones and teeth of ground squirrels frequently 
have been found represented in these deposits (J. Grinnell, MS). The 
remains of two freshly eaten ground squirrels were found in the stomach 
of a wildcat killed in central San Diego County (J. Dixon, MS). 

As to food, the California Ground Squirrel shows a wide range of 
taste, even though there are at the same time decided preferences. He 
cheerfully adopts substitutes when favorite foods are lacking; he is 
not averse to taking considerable barley with his wheat. A list of all 
the plants eaten by the ground squirrel would be a very long one, and 
if locality be taken into account great variation would doubtless be 
found from place to place. The above general statements will be borne 
out, in part at least, by the data presented in the paragraphs to follow. 

On the University campus at Berkeley, on March 13, 1918, the ma- 
jority of the California Ground Squirrels were feeding on the tender 
leaves of alfilaria {Erodium). A female squirrel was observed by the 
junior author at this time to eat the leaves of young plants of the star 
thistle (Centaurea). On San Emigdio Creek, Kern County, on April 
28, 1918, a squirrel was seen to disappear down a hole carrying a sheaf 
of freshly cut heads of foxtail (Hordeum) held tightly in his mouth. 
A few minutes later this squirrel was gassed and when the burrow was 
dug out the fresh foxtail heads were found on the edge of the nest. 
Previously this squirrel was seen to gather heads of both foxtail and 
alfilaria, but preference was given to the latter (J. Dixon, M,S). The 
young as well as the old squirrels seem to prefer alfilaria when obtain- 
able to any other plant. 

In the region about Walnut Creek, Contra Costa County, on July 26 
and August 16, 1918, the authors found ground squirrels feeding exten- 
sively on seeds of bur clover (Medicago hispida). Dried burs of this 
plant were abundant on the hillsides in the near vicinity of the squirrel 
burrows, and although there was a plentiful supply of barley on the 
adjacent stubble fields this was in major part passed up in favor of 
the clover seeds. Hulled seeds of the bur clover were found to pre- 
dominate in the cheek pouches and the stomachs of the score or more 
squirrels that were shot. This fondness on the part of the ground 
squirrels for bur-clover seed suggests a possibly better way of poisoning 
these rodents by using the entire bur of the clover than by the use of 
barley, wheat or other grains, which are now so badly needed for human 
consumption. 

In southern California the seeds of the plant known as wild cucumber, 
manroot, or chilicothe {Echinocystis macrocarpa) is eagerly sought by 
ground squirrels. Gnawed hulls of the seeds of this plant are fre- 
quently found in large quantities near the summits of rock piles where 
the husking or lookout stations of the squirrels are located. In Yosemite 

32 



THE GROUND SQUIRRELS OF CiUjLFORNLV. 



625 



Valley a ground squirrel was seen gathering green fruits from the top 
of a four-foot manzanita bush. 

C. H. Merriam reports (1910, p. 5) that the seeds of the manroot 
{Echinocystis fabacea) are eaten in the vicinity of Modesto from the 
middle of May to the middle of December. The seeds are eaten from 




Fig. 13. Drawings from dissections to show relative extent 
of cheek-pouches in (a) Cahfornia Ground Squirrel and (b) 
Belding Ground Squirrel. One cheek-pouch opens into the 
mouth cavity on each side ; it is lined with membrane contin- 
uous with that lining' the mouth and is used for carrying food 
materials such as seeds and bulbs from the forage ground to 
either the store house or the husking place. It is to be inferred 
that the California Ground Squirrel is much more of a seed- 
gatherer than the Belding. The latter, like the Oregon Ground 
Squirrel, Is more of a grass-eater, and also does not garner 
food 1o the extent that the "digger" squirrels do. 

the time they begin to form until they are fully ripe. "Other favorite 
seeds are those of elderberry {Sambucus) , jimson weed {Datura), wild 
nightshade (Solanum) , turkey mullein (Eremocarpus) , tarweed 
(Madia), and numerous grasses. ... In southern California the 
squirrels are fond of the fruit of the prickly pear (Opuntia).^' 

Ground squirrels are provided with more or less extensive, membrane- 
lined cheek pouches opening inside the mouth, which are used in gather- 
ing and transporting food (see fig. 13). Often when the animals are 
scared out of weed patches or bushes, or away from some supply of roots 



626 THE MONTHLY BULLETIN. 

or bulbs which they have discovered, their cheeks are seen to be bulging 
with the contents of these pouches. They are able to operate their 
teeth and lips even when these pouches are copiously distended. The 
cheek pouches of the California Ground Squirrel are especially well 
developed and this, we think, is correlated with the pronounced seed 
gathering and storing propensities of this species. The following rec- 
ords of cheek-pouch contents, as secured from specimens collected, 
contribute further to our knowledge of the kinds of food of this animal 
and also of the quantity in which these may be gathered. 

A female taken in a stubble field near Walnut Creek, Contra Costa 
County, July 26, 1918, held in her cheek pouches 26 seeds of bur clover. 
A male taken August 15, 1918, at the same place had 78 seeds of bur 
clover and one seed of needle grass. Two other males had one and 
three bur-clover seeds, respectively. Another female taken at the same 
time and place contained 212 seeds of bur clover and 12 seeds of some 
kind of wild grass. Another male held 97 grains of barley and three 
bur-clover seeds. A ground squirrel taken at Cisco, Placer County, on 
October 9, 1913, was carrying 92 seeds of the green manzanita {Arcto- 
staphylos patula) , while a squirrel secured near Pleasant Valley, Mari- 
posa County, on May 28, 1915, had dug up and was carrying in its 
pouches 12 bulbs of a species of wild hyacinth (Brodicea hyacinthina) . 
At El Portal, Mariposa County, a squirrel was secured with three large 
acorns of the golden oak in its cheek pouches. 

We will now consider those feeding habits which make the California 
Ground Squirrel come into conflict more directly with man's interests. 
"Of cultivated nuts, almonds and walnuts are preferred; of other 
crops, apples, prunes, peaches, apricots, figs, olives, . . . the seeds of 
cantaloupes, watermelons and citron melons, and all the grains are eaten 
whenever they are to be had, and green alfalfa and clover are sometimes 
taken" (Merriam, 1910, p. 5). Frank Stephens (1906, p. 66) has 
summed up the food taken by this animal as follows: ''The food is 
principally of a vegetable nature, preferably grain and other seeds, 
fruit, potatoes, green plants, etc. Eggs of poultry and wild birds are 
relished." We have heard considerable testimony from ranchers to 
the effect that individual ground squirrels in different localities have 
learned to raid henneries, so that the above statement is not exceptional. 

A great deal of damage is done by California Ground Squirrels each 
year in orchards and vineyards. The following instances, given by 
Merriam (1910, p. 6) are typical of such depredations. ''Ground 
squirrels are particularly fond of green almonds and of the pits of 
green peaches and apricots, eating these from the time the kernels begin 
to form until the fruit is ripe, thus doing serious damage. They are 
very destructive to apples also, and in places in the foothills of the 
Colfax- Auburn region are said to take fully half the crop. ... In the 
fall of 1907 E. A. Goldman reported that they were doing serious dam- 
age to young vineyards about Orosi, in Tulare County, by biting off the 
leaves and tender shoots of the vines. ... In the orange groves 
between Porterville and Springville, in Tulare County, it is reported 
that they occasionally gnaw the bark of the orange trees and sometimes 
cut the fruit and carry it off. Besides destroying nuts and fresh fruits 
they attack drying prunes and carry off large quantities." 



THE GROUND SQUIRRELS OF CALIFORNIA. 



627 



On May 14, 1918, near the mouth of Caliente Creek wash, Kern 
County, in one corner of a 640-acre field planted to wheat, four large 
bare spots were counted by the junior author in an area of not over ten 
acres. These denuded areas were circular in shape aod averaged 75 
yards in diameter. They were caused by the ground squirrels having 
eaten and destroyed the ripening wheat and even the stalks so that 
nothing but weeds remained. In a single one of these denuded areas 
twenty-three occupied squirrel burrows were counted. In this same 
field, within a six-foot circle the center of which was a lone squirrel 
burrow, 113 heads of wheat were picked up (see fig. 14). These heads 




Fig. 14. These 113 heads of wheat were picked up within a six-foot circle, the center 
of which was a "digger" squirrel burrow situated in the edge of a wheat field. They 
were part of what had been gathered within three or four days, apparently by the one 
squirrel. 

had all been cut and carried to the burrow within three or four days, 
as they were not yet dry. This was evidently the work of a single 
squirrel, since no other squirrel was seen to go near the burrow. These 
113 heads of wheat probably constituted part of what was intended for 
storing, and did not include that required for current consumption. 

In gathering food California Ground Squirrels slink along slowly 
close to the ground, often half hidden in the grass. In gathering ripe 
alfilaria only the clusters of seed cases are taken, with relatively little 
of the stem. However, when the plants are young, the stems and leaves 
are much relished by the squirrels. The usual method of feeding as 
revealed by the binoculars, is for the squirrel to sit up on his haunches 
within reach of the alfilaria heads, which are dexterously gathered into 
little bunches by the front paws of the animal and then quickly snipped 
off by the sharp ineisor teeth. During this last operation the head of 
the rodent is often inclined to one side. In gathering bulky food ma- 
terials such as the heads of foxtail the cheek-pouches are not always 
used, the material being carried crosswise in the squirrel 's mouth directly 
to the burrow. 

On the San Joaquin River near Mendota R. M. Hunt (MS) reports 
seeing squirrels go out into the tules of the sloughs seemingly to eat the 



628 THE MONTHLY BULLETIN. 

green stalks. Several times on following up rustling sounds squirrels 
were discovered on thick mats of dry fallen tules among the standing 
green ones and just above the water. One, on being alarmed, jumped 
into the water with a splash and, although lost to sight, probably 
reached safety by swimming. Davis ^'Island," near Mendota, is part 
of the mainland at low water, but in May, with high water, becomes a 
true island and with the highest water the ground everywhere is com- 
pletely submerged. On June 20, 1918, a squirrel was discovered on 
this island. It jumped from a piece of ground into the water and 
swam, in much the manner of a dog, to a tree up which it took refuge. 




Fig. 15. Metropolis of "digger" squirrels under a small oak on a grain-sown hill- 
side; photographed near Walnut Creek, Contra Costa County, August 15, 1918. 
Owing to the dryness of the season and to the depredations of the squirrels, the grain 
on the hill above the oak had been left uncut. 

A current report was to the effect that each year at high water ground 
squirrels are marooned on this island and live for the time being in the 
big hollow-trunked willows there. This shows that flooding does not 
necessarily drive out or drown these squirrels in such localities as afford 
refuges on high ground or in trees. 

On wild land, alfilaria, foxtail and bur clover are perhaps the three 
plants that are eaten to a greater extent than any other of our forage 
plants. Alfilaria is eaten from the time it appears above ground until 
it ripens, and even after that, when the seeds have scattered out, they 
are gathered and either eaten at once, or stored. The long, curled 
"propellers" are broken off and discarded. In Strawberry Canyon on 
the University campus, in April, the squirrels were harvesting foxtail 
and alfilaria on sunny southern exposures where the plants had matured 
early. Later in the season, during late June and early July, these same 
squirrels with their families of half-grown young were found to have 
moved down the hillsides, some 150 yards, to the moister, shady ground 
near the creek bed where the foxtail was still green, and here they were 
busily gathering the foxtail heads just ripening on July 6. There is 
an obvious rotation in the use of the different important plants for food, 



THE GROUND SQUIRRELS OP CALIFORNIA. 62© 

dependent upon the sequence in which they become available. Thus, 
alfilaria is eaten during winter and early spring ; then the foxtail crop 
claims attention ; and the bur clover, after its seeds ripen, is harvested 
all through midsummer and autumn. Of course the above statements 
are only of local application. 

Examination of the food stores of ground squirrels would go far 
toward providing adequate knowledge of their food habits. Such inves- 
tigations should be made preferably in the fall. Specific information 
now available is as follows: 

In digging out a colonial burrow near Bakersfield, Kern County, on 
May 3, 1918, a storehouse was uncovered. This consisted of a cavity 
or pocket off the main run (see a, fig. 8), which measured five and a 
half by eight inches in two diameters and was eighteen inches beneath 
the surface of the ground. The stored food consisted of a double hand- 
ful of nearly dry heads of foxtail grass carefully packed in dry sand. 
A few alfilaria seeds were also included with the foxtail, but alfilaria 
was scarce at this locality. 

Upward of fifty of the button-like seeds or "cheeses" of the mallow 
(Malva) were observed at the entrance of another burrow at the same 
place, but the observer was unable to determine whether or not these 
seeds were being stored. The mallow seeds were found for the most 
part on the lookout station at the entrance to the burrow. 

"At Modesto in May, 1909, Piper found stores of alfilaria seeds 
packed in cavities and well mixed with dry sand. In December of the 
same year he examined a number of stores of grain unearthed by a 
farmer Avhile scraping and leveling his land. Each of these caches 
consisted of from a pint to a quart of oats stored in cavities and packed 
in dry sand. They varied from 8 to 18 inches in depth beneath the 
surface ; some were in short blind holes ; others at the ends of branches, 
of the main burrow" (Merriam, 1910, p. 5). 

An idea of the quantity of food eaten by the California Ground 
Squirrel can be derived from the following data : 

A female taken near Coulterville, Mariposa County, on June 3, 1915, 
weighed 553.5 grams, or about a pound and a quarter. The stomach 
and its contents alone weighed 77.5 grams, or about 2| ounces (C. L. 
Camp, MS). Figuring out the ascertained weight of the stomach in 
other individuals, 5 grams, the ratio of stomach contents to total weight 
in this squirrel proves to have been about 1 to 7. The material repre- 
sented is presumed to have been fresh green stuff. 

Some experiments have been carried on at the Museum with captive 
squirrels with the purpose of determining the amount of green forage 
consumed daily. Fifty grams, or nearly two ounces, of green alfilaria 
was found to be the average daily ration for an average-sized squirrel. 
In cases where all food had been withheld from the squirrels the previ- 
ous day, the greatest amount of succulent alfilaria, the favorite food of 
the squirrel, consumed in one day was 80 grams, or somewhat less than 
three ounces. 

Five immature ground squirrels taken July 26, 1918, near Walnut 
Creek, Contra Costa County, gave an average total weight of 504.3 
(427.2-517.2) each in grains. The average weight of the stomach con- 
tents in these five squirrels was 13.2 (10.3-19.0), so that the avejrage 
ratio of the weight of the stomach contents to the total weight was 

37 



630 THE MONTHLY BULLETIN. 

1 to 38 (1 to 50-1 to 22). The stomach contents in these cases con- 
sisted almost entirely of finely chewed seeds of barley and bur clover. 
The squirrels were shot between noon and 2 p.m. Seven full-grown 
males taken on August 15, 1918, near Walnut Creek, gave an average 
total weight of 659.4 (576.8-724.7) grams each; the average weight of 
the stomach contents was 17.9 (11.5-20.5) ; and the average ratio of 
contents of stomach to total weight was 1 to 37 (1 to 63-1 to 30). 
Seven full-grown females taken at the same time and place gave an 
average total weight in grams of 500 (370.7-681.4) each; the average 
weight of the stomach contents was 9.7 (5-15.8) ; and the average ratio 
of contents of stomach to total weight was 1 to 42 (1 to 101-1 to 37). 
All these fourteen squirrels were foraging in stubble fields, and the 
stomach contents consisted of barley and bur clover seeds finely chewed 
and of nearly the same degree of moistness as ordinary baker's dough. 
The squirrels were shot between 10 a.m. and noon. 

It is believed by us that two ounces of green forage o r one-half ounce 
of dry grain is an average stomach-full for an average-sized California 
Ground Squirrel and that two stomach-fulls represent a day's ration. 
It is evident that the proportion between the weight of the stomach 
contents and the total weight averages considerably less in this species 
than it does in the Oregon Ground Squirrel. The California is more 
of a seed eater and less of a grass eater than the Oregon Squirrel and 
therefore enjoys a more, condensed ration. 

During late summer digger squirrels, particularly the old adults, 
become exceedingly fat. In this condition they become obviously lazy 
and may often be seen lounging at the entrances to their burrows sim- 
ply enjoying the sunshine. As the season farther advances, a decided 
decrease in squirrel population is noted. The active young of the year 
are still foraging abroad, but even these restrict their activities to the 
brightest hours of sunshiny days. What becomes of the squirrels which 
have altogether disappeared underground? 

One would naturally expect that the life history of such a notorious 
animal as the California Ground Squirrel would be known pretty 
thoroughly. However, such does not seem to be the case ; there are sev- 
eral features of the underground life of this squirrel in regard to which 
our information is very inadequate and of which from the standpoint of 
rodent control it would be most useful to know. As has been previ- 
ously mentioned, little appears to be definitely known regarding the 
period of gestation of this animal. The condition of the young at birth 
and their subsequent care and development is also not well known. 
Another moot point is that of eestivation or hibernation of this species 
of ground squirrel, Merriam (1910, p. 4) states that ''this species 
does not hibernate, except in the mountains, although in the foothills 
and valleys the animals usually stay in their burrows during stormy 
and severe weather. At the upper limit of their range, where the 
ground in winter is covered with snow, they may remain underground 
long enough to be said to hibernate, but over the greater part of the 
state they are out in numbers every month of the year." However, 
we believe we have evidence to indicate that a period of sestivation or 
hibernation (or the two combined), in other words a state of torpidity 
initially induced by the heat and dryness of summer, obtains among 
some at least of the adult ground squirrels even in the lowlands. This 



THE GROUND SQUIRRELS OP CALIFORNIA. 



631 



period of dormancy extends from late summer well through midwinter, 
and thus " gestivation " may be said to go over directly into true hiber- 
nation. The old adults seem to be the only ones that "hole up," for 
the young adults somewhat less than a year old, that is, the young of 
the year, may be seen about the burrows during suitable weather 
throughout the winter. 

In support of the above belief, that a period of torpidity overtakes 
the older individuals of the squirrel population regularly each year, the 
following evidence is submitted : 

(1) Close watch, extending over a period of between four and five 
years, was kept on a female ground squirrel that lived in the dooryard 
at the home of Mrs. Elizabeth Grinnell in Pasadena. This particular 
squirrel did not gestivate until its second year. Then and during each 
succeeding year of its life it cestivated regularly, becoming very fat and 
retiring to its burrow during the last week in August. It emerged 
lean and hungry, with marked regularity, about the twenty-second of 
each following February. When removed from the burrow at intervals 
during this period, the squirrel was found to be in a torpid state, with 
respiration not perceptible. 

(2) In a case in the junior author's personal experience, near Escon- 
dido, San Diego County, all the squirrels that were active in a certain 
field in the fall were poisoned or otherwise killed, and yet old breeding 
squirrels suddenly appeared in this same field the following February. 
This occurred when there was seemingly no possible chance for rein- 
festation from the surrounding fields, which had been cleaned up also. 
Similar testimony has reached us from a number of men identified with 
efforts to exterminate these rodents. 

(3) It occurred to the present writers that it might be possible 
through the examination of specimens to learn the extent to which old 
adults are out in midwinter. The heads of 186 ground squirrels were, 
at our request, secured by the United States Public Health Service, 
shot and trapped near Martinez, Contra Costa County, during January, 
1918, and sent to the Museum of Vertebrate Zoology, where the skulls 
were cleaned and carefully examined. Eelatively advanced age was 
determined from the skulls upon the following criteria: general size, 
zygomatic breadth, breadth of jugals, stoutness of postorbital processes, 
degree of development of sagittal crest, degree of approach of parietal 
ridges, breadth and degree of concavity of frontal surface, advance 
in coalescence of the adjacent bones along certain sutures, and amount 
of wear on the crowns of the molariform teeth. 

The results of our examination are given in Table II : 

Table II. Proportions of adult to young ground squirrels abroad in midwinter. 



Date received (in 1918) 



Total 

number of 

skulls 



Number | Number I Ratio of 
of old of young old adults 

adults I adults to total 



January 8 : 18 

January 14 j 34 

January 22 I 86 

January 24. ...j 48 



1 to 18 
1 to 8.5 
1 to 4.7 
1 to 4.3 



The foregoing data are not nearly as complete as could well be desired, 
but as far as they go they show that "old adult" squirrels are relatively 



39 



632 THE MONTHLY BULLETIN. 

scarce aboveground in January as compared with the younger animals, 
those probably less than one year old. Further, the proportions of old 
to young increases rapidly towards the last of that month; in other 
words, as the breeding season approaches. It is probable that the full 
old-adult population is not abroad aboveground until the last of Feb- 
ruary, when the ratio of old adults to young of the previous year would 
certainly not be nearly so little as 1 to 4, which is the mi Qimum possible 
at the immediate close of the breeding season. 

In spite of the above lines of evidence, the real extent of this habit of 
aestivation among our ground squirrels is not satisfactorily known. It 
is exceedingly difficult to follow any individual squirrel under perfectly 
normal conditions through all its various activities for any great length 
of time. However, an important factor concerned in the work _ of 
destroying these animals is suggested ; that is, the des irability of placing 
emphasis upon the need of poisoning in the spring rather than in the 
fall, when part of the breeding stock may be stowed away out of the 
reach of poisoned grain. It is a question, too, whether or not a dormant 
animal, in which respiration is extremely slow, would be fatally injured 
by a fumigant before the latter would be dissipated. 

Human interest in the California Ground Squirrel nat arally concerns 
itself most especially with the questions of total population, rate of 
increase, and rate of re-invasion of territory previously cleaned of squir- 
rels. As to the first question, we have found it difficult to find an 
accurate basis for determining the squirrel population living on any 
given imit of area, such as an acre or a square mile. Counts may be 
taken of living squirrels that happen to be aboveground at any one time, 
or of burrows which give evidence of current use. In the first ease 
the count is never likely to cover all of the squirrels i n tlie area, because 
the chances are overwhelmingly against all of the squirrels being above- 
ground at one time. Season of the year, time of day, and state of 
weather will affect profoundly this proportion of squirrels below ground 
to those in sight. In the latter case some sort of estimate of ratio of 
squirrels to burrows must have been arrived at. Season of the year 
must again figure importantly in the estimate, because of the jump in 
population following the breeding season, and progressive decrease 
thereafter. 

On July 26, 1918, the authors took two censuses of ground squirrels 
on a badly infested ranch about three miles northwes t of Walnut Creek, 
Contra Costa County (see fig. 16). The first census was taken on a 
south-facing hillside on an area 100 feet square, approximately one- 
fourth of an acre. Three counts gave 19, 16 and 17 squirrels, respec- 
tively, in sight at once. Twenty-five open burrows were counted in 
this area. This, therefore, was at the rate of 76 squirrels and 100 
burrows per acre, or 1| burrows to each squirrel. The breeding season 
at that date was well passed. Allowing one adult to every four young 
gave fifteen adults to every 100 burrows or between six and seven open 
burrows to each adult squirrel after the breeding season. 

The second census was taken in a mowed field from which a crop of 
barley hay had been recently harvested. The area taken was on a north 
slope and measured 250 feet square, covering about 1^ acre. Three 
counts were taken between noon and one o'clock. The number of squir- 
rels seen out at once was 25, 26 and 25, respectively. Sixty burrows 

40 



THE GROUND SQUIRRELS OF CALIFORNIA. 633 

were counted in this area, so that the infestation was at the rate of 20 
squirrels and 50 holes per acre. This is at the rate of 2^ burrows to 
each squirrel. 

On May 28, 1918, a single isolated colony was investigated at a point 
twelve miles west of Fresno. This colony was in a plowed field which 
had been planted to grain for several years past. Here, in an area 100 
feet square 16 squirrels, eight of which were less than half grown, and 
17 burrows were counted. The ratio here was close to one burrow to 
each squirrel. This figure, again, applies to a period after the close 



1^ 


^^ 


. ^.^ 






-^^^M 




m^^ ^ - ^f~iss 




^^H^^^^^^^^^^^B^K^^ '■sA^^S^,'^^^-'' ^ 


s^lbi^..::-. mm 







Fig. 16. Hillside near Walnut Creek, Contra Costa County, badly infested with 
"digger" squirrels. On August 15, 1918, squirrels were here present at the rate of 
fifty per acre. From this breeding ground they were at this time invading the grain 
fields on the opposite slope. 

of the breeding season, when the squirrel population had reached its 
maximum. 

Counts taken before the breeding season naturally give different 
results. At Berkeley on March 13, 1918, the junior author counted 47 
squirrel burrows in a colony which occupied about one acre on a hillside. 
By counting the squirrels which appeared aboveground in this area on 
several successive days it was ascertained that there were about nine 
adult squirrels inhabiting this acre of ground. This gave an average 
of over five burrows to each squirrel. 

The above-cited instances are based on maximum infestation. Local 
distribution is often very irregular, since squirrels may be abundant on 
the southern exposure of a hill and yet be entirely absent on brushy 
northern slopes only a hundred yards or so distant. Even on the plains 
and in the valleys, although the distribution is much more uniform, 
there is often marked unevenness in infestation irrespective of human 
interference. Surgeon John D. Long (1912, p. 1596), in comparing 
the cost of the various methods of destroying ground squirrels, based 
his estimates of cost on an infestation of ten holes per acre. Presum- 
ably, this was taken as representing an average infestation according to 



634 THE MONTHLY BULLETIN. 

the experience of the United States Public Health Service in their 
eradication work. This appeals to us as a fair estimate on well-popu- 
lated territory, such as that around San Francisco Bay. 

It is the authors' belief that if the entire area in California occupied 
by this species be taken into consideration a population of one squirrel 
per acre, or 640 per square mile, at the conclusion of the breeding season, 
would be a fair average. At this rate there would be a total population 
of 32,000,000 California Ground Squirrels in the state in July, and one- 
fourth this, or 8,000,000, in March, before the young of the year are out. 
If the closely allied Fisher and Douglas ground squirrels be included, 
as from an economic standpoint might well be done, the ' ' digger squir- 
rel" population of the state in summer, when crops are maturing, may 
be put at between 40 and 50 millions, in this state. 

As for rate of increase, we are dealing with a prolific animal. As 
already shown, the average size of the litter in the California Ground 
Squirrel numbers practically eight. Males and females are present in 
a general population in about equal numbers. Even though but one 
litter is reared by each female squirrel each year, this would mean that 
for each pair of squirrels at the beginning of the breeding season there 
will be ten individuals at the close of the breeding season. The evidence 
we have examined goes to show that all the squirrels breed the first year 
of their lives — that is, when each is not quite one year old — as well as 
subsequently, and that the life-time of a squirrel, if it dies of old age, is 
five years. If we do not count upon any fatalities, one pair of squirrels 
can be reckoned on to give origin to a population in five years of 6,250 ! 

In recent efforts to eradicate squirrels a 90 per cent efficiency has 
been currently estimated. This means that, if no follow-up campaign 
be waged, ten squirrels out of each original 100 will be left, to form a 
nucleus of future increase. At the end of the second year the popula- 
tion would be back to normal. Supposing, further, that a follow-up 
campaign is waged at the end of a suitable interval before the next 
breeding season, also with a 90 per cent effectiveness; then only one 
squirrel per original hundred would be left. Even then, when only 
six squirrels are left on one square mile, these in the third breeding 
season will produce, barring normal fatalities, the original 640, with 
a good margin to spare. 

The factors limiting the population of ground squirrels under nat- 
ural conditions, that is, as not affected by human agency, include the 
following, in the order of probable importance: (1) Quantity of food 
available at the season of the year when food is scarcest; (2) natural 
enemies, including predatory mammals, birds and reptiles; (3) adverse 
weather conditions, recurring rather infrequently, as when territory is 
inundated during exceptionally heavy rains; (4) disease; (5) old age. 
The rate of increase, through long ages, has been adjusted to more than 
meet the expected death rate from all causes combined. This rate of 
increase, fourfold each year, is now inherent and we have no reason 
for expecting any abrupt and permanent change in it either way. 

"With the arrival of the white man and his accessories in California, 
the natural balance has been upset. Man has destroyed a large per- 
centage of the natural enemies of the ground squirrel. Cultivation of 
the land has, on the other hand, in portions of the state improved the 
food supply. The general tendency is for the squirrels to breed up on 



THE GROUND SQUIRRELS OF CALIFORNIA. ' 635 

uncultivated land where they are least molested through human agency, 
and from this they spread out and invade nearby cultivated fields. 
The process is most conspicuously in evidence during late summer con- 
sequent upon the emigration of the young of the year, this being in 
compensation for the tendency to congestion of population brought on 
during the breeding season. 

Reduction in the food supply locally causes the squirrels to spread 
out in search of new pastures. Such movements are usually less than 
a mile in extent, and of course come particularly to notice in the vicinity 
of grain fields and orchards to which the squirrels drift at the time the 
crops begin to ripen. Some idea of the rate with which ground squirrels 
reinfest cultivated fields which are adjacent to wild land may be had 
from the following instance. Mr. 0. N. Garrison of Earlimart, Tulare 
County, stated in an intervicAV that during the spring of 1918 thirty-six 
ground squirrels were drowned out on a five-acre field of alfalfa at the 
first irrigation and this in spite of the fact that the field had been free 
from squirrels at the end of the previous irrigation season in the fall 
of 1917. 

From the earliest times of which we have record to the present day 
the California Ground Squirrels have given the impression of abun- 
dance. Changes in the status of the species within history have only 
concerned local occurrence. There is nothing to show that there has 
been any extension of the general range of the species, or any retraction 
in it either. As already set forth, the arrival of the white man and the 
institution of agriculture has undoubtedly had the effect locally of 
increasing the ground squirrel population. On the other hand, where 
man has been aroused by the seriousness of their depredations to the 
point of adopting and putting into force effective means of control the 
numbers of the squirrels have been conspicuously reduced. Thus at 
Earlimart on May 16, 1918, ground squirrel burrows were found to be 
abundant over a large acreage of "hog wallow" land. Live squirrels, 
however, were exceedingly scarce, only five being found on one tract of 
forty acres which had been thoroughly poisoned the previous season. 
A count taken on this tract showed that there was an average of fifty 
empty burrows to each squirrel present. 

A very few localities have been reported in which the squirrels are, 
for the time being at least, things of the past; but the possibility of 
re-invasion presents itself, and this, as already shown, may be a very 
rapid process. It would seem that ground squirrels, like weeds or 
scale bugs, will have to be watched continually, and proper measures 
taken whenever necessary to prevent the reinfestation of land which is 
thought to have been freed. 

The difficulties in arriving at a fair estimate of the damage done by 
the California Ground Squirrel, which is by far the most injurious 
species in the state, are many and various. We have tried to get at 
a satisfactory estimate (not a guess) in terms of dollars per annum, 
but have not succeeded. It may be of some interest, however, to give 
some other figures, indicative in partial degree of the loss that may be 
occasioned by this ground squirrel. 

In order to ascertain the bearing of squirrels upon grazing interests 
we have found some basis for estimating squirrels in terms of live- 
stock. We have weighed and examined the stomach contents of a series 



636 THE MONTHLY BULLETIN. 

of squirrels, with results already given. These, summarized, show that 
one ounce of dry grain or seeds, or four ounces of green vegetation, is 
consumed each day by an average California Ground Squirrel. If we 
take fifty pounds of green stuff as representing the amount of forage 
consumed daily by one steer on open range, then 200 squirrels would 
appropriate the forage which would keep one steer. Twenty squirrels 
would eat as much as one sheep, and this last estimate would be most 
significant, because sheep graze closer and hence the competition here 
would be sharpest. 

Expressing this relationship in another way, taking the average popu- 
lation of ground squirrels on open range as one per acre or 640 per square 
mile, the squirrels on each square mile appropriate the forage of three 
steers or 32 sheep. If the entire range of the California Ground 
Squirrel be taken into account and be supposed to consist purely of 
grazing lands (and so of minimum land value) grazed to their fullest 
capacity, then the squirrels of this species take the place of 160,000 
cattle or 1,600,000 sheep. Of course, it is not likely that the squirrels 
come into actual close competition with livestock in ordinary years ; but 
in extra dry years, such as that of 1917-18, when all the living things 
which depend on vegetation for support are hard pressed to maintain 
existence, then the squirrels cannot help but crowd the cattle interests 
of the country, which are of such vital human importance. 



FISHER GROUND SQUIRREL. 
Citellus beecheyi fisheri (Merriam). 

PLATE V. 



Other names. — Fisher Spermophile ; Digger Squirrel, part; Spermophiltis beecheyi, 
part; 8permophilus heeclieyi fisheri; Spermophilus grammurus -fisheri; Citellus 
varicgatns fisheri; Citellus grammurus fisheri; Otospermophilus beecheyi fisheri; 
Spermophilus grammurus beecheyi, part. 

Field characters. — As for the Beechey Ground Squirrel, differing in paler tone of 
general coloration, and in more extensive and purer white shoulder patches. Length 
of body alone about 9| inches, with tail about 6 inches more. 

Description. — In all pelages: Closely like beecheyi, except for pallid tones of 
color predominantly light cinnamon-drab, and extension of light areas. The shoulder 
patches in typical fisheri are much clearer white and tend to meet on the fore back 
between the shoulders ; in some specimens the mid-dorsal grayish brown stripe is 
almost obliterated by these white invasions. The back of the ear is usually grizzled 
buffy in fisheri instead of chiefly black, and its hinder margin and base are silvery 
white. The lower surface of the body and the upper surfaces of the feet are usually 
much whiter, less buffy, than in beecheyi. 

Color variations. — The range of individual and seasonal variation in fisheri seems 
to be about the same as in beecheyi. 

The extreme of the characters of fisheri are developed in the Inyo region, and grad- 
ual intergradation or blending takes place towards beecheyi chiefly through southern 
Tulare aud Kern Counties. The dotted line on the map (fig. 17) separating the ranges 
of fisheri and beecheyi represents no place of abrupt demarcation but only somewhere 
near the middle of the belt of intergradation. Many individuals from the vicinity 
of this hypothetical line are so nearly betwixt typical beecheyi and typical fisheri 
that they can only arbitrarily be placed under one name or the other. This has been 
done with such intermediate examples in the lists of specimens examined. 



THE GROUND SQUIRRELS OP CALIFORNIA. 637 

Measurements. — Average and extreme measurements, in millimeters, of thirteen 
mature specimens from Inyo County are as follows : Five males : total length, 417 
(400-455) ; tail vertebrae, 163 (155-180) ; hind foot, 57 (50-65) ; ear from crown, 
19 (16-22) ; greatest length of skull, 55.4 (54.1-57.0) ; zygomatic breadth, 34.7 
(33.3-36.3) ; interorbital width, 13.3 (13.1-13.9). Eight females: total length, 396 
(374-417) ; tail vertebrae, 157 (145-170) ; hind foot, 53 (51-55) ; ear from crown, 
19 (18-23) ; greatest length of skull, 53.9 (52.3-55.7) ; zygomatic breadth, 33.2 
(31.0-34.7) ; interorbital width, 13.2 (12.2-14.3). 

The above figures show that the race fisheri is decidedly smaller 'n almost every 
particular than ieecheyi. The disparity between the sexes is quite as well shown, 
however, and the rest of the variable features seem to be exhibited in about the 
same degree, making due allowances for the smaller number of fisheri measured. 

Weights. — Average and extreme weights in grams r.f eight mature specimens from 
Inyo County are as follows : Five males, 589 (480-656) ; three females, 400 
(321-440). Averages in ounces: males, about 20f ; females, about 14. 

It is probable that a larger series of weights would give somewhat different averages. 
That for the females seems low. 

Type locality. — Kern Valley, 25 miles above Kernville [^ South Fork of Kern 
River 25 miles east of Kernville], Kern County, California (Merriam, 1893, p. 133). 

Distribution area. — Roughly the western borderlands of the Mohave Desert, north 
into the Inyo region and south as far as the northwestern arm of the Colorado 
Desert. More in detail, the western side of Owens Valley including the adjacent 
east slopes of the Sierras north to the vicinity of Mammoth Pass ; east from the south- 
ern end of Owens Lake through the Coso, Argus and north end of the Panamint 
Mountains ; the extreme southern Sierras, including the entire drainage basin of the 
Kern River ; the southern end of the San Joaquin Valley south of Tulare Lake, 
and the Carrizo Plains country and adjacent hills and valleys to the westward ; the 
Tehachapi, Tejon, San Bernardino, San Jacinto and Santa Rosa Mountains and 
adjacent desert borders. The approximate line of blending between the races beecheyi 
and fisheri is shown on the map (fig. 17). With regard to life-zone the Fisher Ground 
Squirrel extends from the Lower Sonoran to the Canadian but its greatest nurabe"s 
are reached, and most of its habitat lies, in the Upper Sonoran (see fig. 23). 

Specimens examined. — A total of 96 specimens from the following localities, all 
in California : Inyo County : Little Onion Valley, 7,500 ft., east slope Sierra Nevada 
west of Independence, 1 ; Independence, 4 ; vicinity of Lone Pine, 3 ; vicinity of Jack- 
ass Spring, 6,200-6,500 ft, northern part of Panamint Mts., 9; Little Lake, 2 
Olancha, 1 ; Little Cottonwood Creek, at 10,000 ft. alt., 1. Tulare County : Jordan 
Hot Springs, 6,700 ft., 1 ; Jackass Meadow, 7,750 ft., 1 ; Trout Creek, 6,000 ft., 3 
Taylor Meadow, 7,000 ft., 5; Cannell Meadow, 7,000 ft., 1; Earlimart,'2 ; Tipton, 5, 
Kern County : Kern River, seven miles above Kernville, 1 ; Fay Creek, 4,100 ft., 2 
west slope Walker Pass, 4,600 ft., 3 ; Weldon, 1 ; Isabella, 2 ; Bodfish, 1 ; Kern River, 
twelve miles below Bodfish, 1 ; eight miles northeast Bakersfield, 1 ; San Emigdio, 2 
Fort Tejon, 5. San Luis Obispo County : near Simmler, on Carrizo Plains, 1. Ven- 
tura County : Mount Pinos, 3. San Bernardino County : Victorville, 2 ; Cushenbury 
Springs, 1; Doble, 7,000 ft., San Bernardino Mts., 1; Bluff Lake, 7,500 ft., San 
Bernardino Mts., 2 ; F'sh Creek, 6,500 ft., San Bernardino Mts., 1. Riverside 
County ; near Banning, 1 ; Cabezon, 9 ; Snow Creek, near Whitewater, 1 ; Schain's 
Ranch, 4,900 ft, San Jacinto Mts., 4 ; Fuller's Mill, 5,900 ft, San Jacinto Mts., 1 ; 
Round Valley, 9,000 ft, San Jacinto Mts., 1 ; Tahquitz Valley, 8,000 ft., San Jacinto 
Mts., 1; Strawberry Valley, 6,000 ft, San Jacinto Mts., 9. 

The Fislier Ground Squirrel is closely related to, and in general 
very much like, the California Ground Squirrel with which it blends 
in Kern and Tulare Counties. In general appearance the former is 
slightly smaller and decidedly paler than the latter. The Fisher Squir- 
rel may be recognized in the field by its extensive white shoulder 
patches. This sub-species is also known as "digger" squirrel. 

The range of the Fisher Squirrel includes Kern Valley and part of 
Owens Valley, the extreme southern part of the San Joaquin Valley, 
and a strip of territory along the northern and western edges of the 

" 45 



638 



THE MONTHLY BULLETIN. 



Mohave Desert from the mountains east of Owens Lake south to the 
Santa Rosa Mountains west of Salton Sea. 

In altitude this squirrel ranges from 450 feet, as at Palm Springs 
at the eastern base of San Jacinto Peak, to 10,500 feet, as within a 
quarter of a mile of the summit of the same mountain (H. S. Swarth, 
MS). It is to be found from the southernmost plains of the San 




Fig. 17. Map showing California distribution of the California, Fisher, Catalina 
Island and Douglas ground squirrels, and the Rock Squirrel, all being of the "digger" 
category. The spots represent localities from which actual specimens have been 
examined. 

Joaquin Valley to 10,000 feet altitude in the Mount Whitney region. 
This rodent thus shows little regard for zonal limitations, occurring all 
the way from the Lower Sonoran zone to the Canadian zone, though 
its numbers above the Upper Sonoran are small. It is equally at home 



THE GROUND SQUIRRELS OP CALIFORNIA. 639 

in the cultivated fields in the irrigated sections, about Bakersfield and on 
the rocky ridges of the Panamint Mountains. 

At Jackass Springs, in the Panamint Mountains, Inyo County, on 
October 5, 1918, eight Fisher Ground Squirrels were counted in a three- 
hour census in the belt of sagebrush and piiion. These were invariably 
perched upright on the summits of gray granite boulders. They were 
even then notably pale-colored, with teecheyi in mind (J. Grin- 
nell, MS). 

At Mount Pinos, Ventura County, during the first week in July, 
1904, Fisher Squirrels were present from the very summit (8,826 feet) 
down. They were trapped among the rockpiles near the top, and on 
the smooth slopes among the firs on the north side. Young were num- 
erous, and quite unsuspicious, being run down with ease when caught 
a little ways from their retreats (J. Grinnell, MS). 

Near Lone Pine in Owens Valley on June 16, 1917, Fisher Ground 
Squirrels were found inhabiting the lower embankment of the Los 
Angeles Aqueduct. At one point three miles south of Lone Pine, some 
thirty squirrels were noted along the aqueduct in a distance of half a 
mile. Other colonies were found along Lone Pine Creek at the edge 
of an old orchard (A. C. Shelton, MS) . 

In the region about Bakersfield Fisher Squirrels were found in con- 
siderable numbers near the mouth of Caliente Creek east of Bakersfield 
both in the wheat fields and on the adjoining plains covered with a low 
growth of cactus. In the irrigated region southwest of that city the 
squirrels were locally numerous on pasture land. 

The Fisher Ground Squirrel as far as we can see is indistinguishable 
from the California Ground Squirrel in many particulars such as 
behavior, voice and mannerisms. This statement applies also to the 
general feeding and breeding habits of the form. Many incidents 
bearing on such points as enemies and natural checks have been 
recounted in our chapter relating to leecheyi, since they are for the 
most part identical in the two races. 

Certain instances of behavior in the desert race seem worthy of 
special mention. At Isabella, Kern County, on July 4, 1911, W. P. 
Taylor (MS) states that it was a common thing to see the squirrels up 
from the ground in guatemotes or willows. At Palm Springs, River- 
side County, on February 4, 1916, two Fisher Squirrels were seen to 
leap an irrigation ditch near town, a clear jump of about four feet 
(H. S. Swarth, MS). Sometimes individuals of this species do not 
hesitate to jump into water and swim, so as to escape from enemies. 
At Onyx, Kern County, on June 19, 1911, a half-grown squirrel was 
surprised on the bank of an irrigation ditch which was full of water. 
The stream was six feet wide, with rapid current. Without the least 
hesitation, the squirrel precipitated itself into the water and swam 
across, reaching the opposite shore by a diagonal down-stream course. 
It then quickly ran to a burrow, with the location of which it seemed 
familiar and from which it is likely to have come originally and crossed 
the ditch of its own accord for the purpose of foraging (J. Grin- 
nell, MS). 

The time of birth of the young in this species varies with altitude, 
more precisely zone, from April to late in June. At Cabezon, River- 
side County, a one-third grown young one was secured May 16, 1908, 



640 THE MONTHLY BULLETIN. 

while at 8,500 feet on Mount Pinos, Ventura County, a similar sized 
young one was taken July 11, 1904, At the former locality three juve- 
niles and an adult female were drowned out of one community burrow in 
an almond orchard. This is probably about the minimum number in a 
litter, as the average number of young in a litter appears to be only 
slightly less than in the California Ground Squirrel. ''The average 
number ... of young at a birth . , . along the borders of the Mohave 
Desert appears to be ... 6 or 7" (C. H. Merriam, 1910, p. 4). At 
Schain's Ranch, San Jacinto Mountains, on June 18, 1908, a family of 
eight young ground squirrels was observed aboveground at one time 
at the mouth of a burrow (W. P. Taylor, MS). 

Regarding food preferences of this sub-species a special feature has 
been noted with extraordinary frequency, as follows. Many Fisher 
Ground Squirrels are taken in meat-baited steel traps set for predatory 
carnivores under circumstances which make it seem certain that they 
were caught while trying to steal the bait. They have also been knowTi 
to eat woodrats and even other individuals of their own kind which 
they have found dead in traps. 

At Kelso Pass, Kern County, on July 8, 1911, two Fisher Ground 
Squirrels came to drink at a seepage from a spring. One drank six 
times, the fifth time for over two minutes, by count of seconds (J. 
Grinnell, MS). 

The following records of cheek-pouch contents establish some of the 
sorts of food taken by this animal. At Taylor Meadow, Tulare County, 
a squirrel was taken on July 25, 1911, with 88 seeds of a lupine 
(Lupinus grayi) in its cheek-pouches. Another squirrel taken seven 
miles above Kernville, Kern County, on June 26, 1911, was carrying 
a seed of the Digger Pine {Pinus sabiniana) ; while a third squirrel 
taken at Lone Pine, Inyo County, had gathered and placed in its cheek 
pouches 118 seeds of Encelia frutesceiis and 5 seeds of Hymenoclea 
salsola. 

Squirrels of this subspecies were found doing a large amount of dam- 
age to the almond crop at Cabezon, Riverside County, on May 16, 1908. 
Here they were living right in the almond orchard, most of the inhabited 
burrows being dug close to the roots of the trees. Other short, shallow 
burrows were noted, but these were thought to be of use only for tem- 
porary protection in case the animals were taken by surprise (C. H. 
Richardson, MS). 

In Antelope Valley, near Fairmont, Los Angeles County, on June 22, 
1904, the authors found ground squirrels doing enormous damage to 
almonds, climbing the trees and biting open the green fruit to take out 
the pit and often leaving the hull in place on the tree. The pit was 
frequently found to have been removed from a remarkably small hole 
in the side or end of the shell. 

At various points within the range of fisheri we have been told by old 
residents that digger squirrels have only recently invaded the locality 
and that a few years ago there were none where many squirrels are now 
present. In many such cases the sudden increase in the number of 
ground squirrels is evidently due not to invasion from without, but to 
the breeding up, under favorable conditions, of the local stock of squir- 
rels which have been present all the time, but which was formerly so 



THE GROUND SQUIRRELS OP CALIFORNIA. 641 

small and scattered that it did not attract attention. A typical example 
is as follows. 

Residents of Owens Valley at Lone Pine stated in June, 1917, that 
the ground squirrels there had only recently invaded the valley and that 
none were known i a that vicinity five years before. But from this same 
locality specimens now preserved in the Field Museum of Natural His- 
tory in Chicago were obtained in 1902, fifteen years previously. 
Although the squirrels are said to be steadily increasing along the west 
side of Owens Valley, little or no effort appears to have been attempted 
at controlling the pest. 

At the Carl Walters Ranch, two miles north of Independence, on 
June 26, 1917, Fisher Ground Squirrels were found to be fairly abun- 
dant on both this and most of the other ranches in the vicinity. They 
had been considered a nuisance here for a number of years (A. C. 
Shelton, MS). 

The irrigation and cultivation of extensive areas have resulted in a 
greatly increased available food supply which has proven acceptable to 
the ground squirrel and has resulted in greatly increasing its popula- 
tion. It is the authors' belief that the squirrels have been present in 
Owens Valley from time immemorial and that as long as they were 
few in numbers and stuck to the rocky, uncultivated ground they 
remained largely unnoticed, but that when they invaded irrigated 
fields and became numerous they attracted attention and were then 
thought to have but just moved into the valley. 

It is believed that, on the whole, there are only about half as many 
Fisher Ground Squirrels to the square mile throughout its range as 
there are California Ground Squirrels to the same unit of area in the 
range of that form. Fisher Squirrels nevertheless prove very destruc- 
tive locally to cultivated crops. Many small isolated orchards and 
"dry-farmed" grain fields are scattered throughout the western and 
northern parts of the range of fisheri and these frontier ranches are 
the ones which suffer. While the money value of the crop destroyed 
may be small, yet such crops are often the settler's principal means of 
obtaining a livelihood and, although this may be humble indeed, its loss 
is felt critically. It is the authors' belief that the Fisher Ground 
Squirrel ranks third, or next after the Oregon Ground Squirrel, in point 
of economic importance in California. 



CATALINA ISLAND GROUND SQUIRREL. 
Citellus beeeheyi nesioticus Elliot. 



other names. — Island Spermophile ; Citellus nesioticus; Spermophilus ieecheyi, 
part. 

Field characters. — A.s for the Beechey Ground Squirrel. Only to be distinguished 
from it on comparison of series of specimens; coloration averaging darker, general size 
greater, and tail relatively shorter. Length of bod" alone, -n males, about Hi 
inches; w'th tail (without hairs) about 71 inches more. 

Description. — Adults in April: Similar to the Beechey Ground Squirrel (San 
Francisco Bay region) as already described, but general coloration darker; top of 
head from nose to nape, and bi'oad area down middle of fore back between light 



642 THE MONTHLY BULLETIN. 

shoulder patches, deep cinuamou-brown, the hairs individually being black, tipped with 
cinnamon ; middle of back darker in tone than top of head ; spot above upper eyelid 
blackish ; cheeks and sides of neck much darker in tone than in beecheiji; vphitish 
shoulder patches, restricted in exten% dull and indistinct as compared with fisheri and 
douglasii, even more so than in heeclieyl. Under surface of body very dark in tone, 
the hairs extensively grayish bister at bases and tipped with cinnamon buff. Tail 
and feet colored as in heecheyi. 

Color variations. — The type and one other specimen show a black patch on the 
crown, due to lack of cinnamon hair-tippings ; this, of course, is merely an individual 
feature. 

The May-taken series at hand shows various transition stages from winter to sum- 
mer pelage. In most of the specimens the fore parts are in fresh harsh summer coat, 
while the rump is still covered with the winter coat, showing underfur, and being 
more or less worn and faded. The tail in some examples is markedly worn and faded, 
with the usually resulting changes in color. In some specimens the hairs of the 
tail show but two dark bands instead of three ; but this variation occurs also in 
other near-related races of ground squirrels. The two skins taken in February are in 
full winter pelage, showing more or less underfur over the whole body and no signs 
of molt. The fore parts, as compared with the summer pelage, are less bright in 
color tones, and the shoulder patches are even less distinctly whitish. Hinder upper 
surface and tail exactly as in heecheyi of same season. 

Measurements. — Average and extreme measurements, in millimeters, of nineteen 
full-grown specimens from near Avalon, Catalina Island, are as follows : Seven 
males: total length, 471 (447-495); tail vertebraj, 189 (175-200); hind foot, 
59 (55-63) ; greatest length of skull, 60.2 (56.1-63.7) ; zygomatic breadth, 36.9 
(33.8-39.2) ; interorbital width, 14.8 (13.3-15.9). Twelve females: total length, 444 
(406-475) ; tail vertebrae, 179 (161-194) ; hind foot, 56 (53-62) ; greatest length of 
skull, 57.7 (54.0-62.4) ; zygomatic breadth, 35.9 (33.3-37.6) ; interorbital width, 
14.3 (13.0-15.4). 

Close examination of the series of skulls shows to us no character by which to 
tell them from heecheyi or fisheri except for average greater size. There is the 
usual range of variation in proportions, due to age, this factor being judged from 
degree of wear on the crowns of the molariform teeth. Old skulls are largest, 
broadest relatively to length, and with most prominent ridges and processes. It is 
difficult for us to understand how Elliot (1904, p. 263) could have assigned the 
numerous cranial characters he did to the form he named, except on the ground that 
he examined but a very few specimens of heecheyi and fisheri and that these 
happened to be extreme. 

Type locality. — Santa Catalina Island, California (Elliot, 1904, p. 263) ; more 
exactly, vicinity of Avalon, according to the collector of the type, Mr. John Rowley, 
in interview. 

Distribution area. — Santa Catalina Island, California. Life-zone, Upper Sonoran. 

Specimens examined. — A total of 21 skins and skulls, all from the vicinity of 
Avalon, Catalina Island. Two of these (including the type) were loaned us from the 
Field Museum of Natural History, Chicago ; and nineteen were loaned us from 
the Museum of History, Science and Art, Los Angeles. 

Only three species of rodents are known to be native to Catalina 
Island, a harvest mouse, a white-footed mouse, and the Catalina Island 
Ground Squirrel. This last-named animal is, as in each of the other 
cases, but slightly differentiated from its counterpart on the adjacent 
mainland. With little doubt it differs no more from its near relative, 
the Beechey Ground Squirrel, in general habits and traits, than it 
does in structure. 

Until the present year very little has been known of the Catalina 
Island Ground Squirrel. In fact, the original characterization of the 
race was so unsatisfactory as to leave doubts in the minds of some 
students as to whether the island animals really differ at all from the 



50 



THE GROUND SQUIRRELS OP CALIFORNIA. 643 

mainland ones. Fortunately for the present writers, our appeal to Mr. 
Frank S. Daggett, Director of the Museum of History, Science and 
Art, in Los Angeles, was promptly met by action, and Mr. L. E. Wyman 
of Mr. Daggett's staff was detailed to go to Catalina and obtain a suffi- 
cient number of specimens for deciding the doubtful questions. Mr. 
Wyman was eminently successful, and the resulting series of .skins and 
skulls, together with the accompanying information, was freely placed 
at our disposal for use in connection with the present paper. 

Mr, Wyman found the squirrels fairly swarming May 9 to 16, 1918, 
at the upper end of a narrow tract of bottom land about a mile back 
of Avalon. This tract, dotted with elderberry trees, had been seeded 
to barley, and the grain stood knee-deep except in the spots where it 
had been persistently eaten down by the squirrels. The hillside adjoin- 
ing on the northwest was steep and fairly well covered with cactus and 
chaparral, and in places it was honeycombed with burrows. The bottom 
of the hill was beset with extensive diggings every fifty feet or so. 

Besides the barley, the squirrels were feeding on a variety of wild 
vegetation. Each of the numerous stomachs examined contained a well- 
chewed green mass. Cheek-pouches were found to contain barley blades 
and certain seeds, and in one case four bulbs of ''sour-grass" or "grass- 
nuts" (Brodicea capitata), the largest of which was half an inch in 
greatest diameter. These bulbs seem to be specially sought after, as 
several small areas were found, usually on south-fronting grassy hill- 
sides, where the ground was all dug up by the animals, and hulls of 
Brodicea bulbs were lying about. 

One ground squirrel was seen at work in a wild tobacco tree about 
seven feet from the ground. He had gnawed at the stem near the top 
until only a shred kept it from dropping. Gnawed shells of chilicothe 
seeds were also found. 

Mr. Wyman believes that the notes and actions of the Catalina 
Island Ground Squirrel do not differ to any appreciable extent from 
those of the mainland Beechey. The island animals were perhaps 
slightly less noisy, though when once started to barking they seemed 
hardly able to stop. They were found to be shy on open ground, 
hustling to cover when the invader of their domain was yet 200 yards 
off. By sitting quietly under a tree, however, Mr. Wyman had one 
squirrel approach him to within ten yards and feed on barley shoots. 
On the brushy hillsides, the collector was able to stalk his quarry with 
ease. 

All the females taken were notably fat, and none contained embryos. 
Also no young of the year were seen; so that it would seem that the 
breeding season of the island squirrel is much later than that of the 
mainland animal — later, at least, than May 16. Every specimen taken 
by Mr. Wyman was "loaded with fleas;" these, however, quickly dis- 
appeared and in no case caused any annoyance to the collector. 

Since ground squirrels were seen by the senior author commonly in 
August, 1903, in the vicinity of the Isthmus, near the northwest end 
of Catalina, it may be inferred that the animals are widely distributed 
over this island. No species of ground squirrel whatever exists native 
on any of the other California islands. 



644 THE MONTHLY BULLETIN. 

DOUGLAS GROUND SQUIRREL. 
Citellus douglasii (Richardson). 

PLATE II. 



Other names. — Douglas Spermophile ; Digger Squirrel, part; Arctomys douglasii; 
Citellus douglasii; Citellus variegatus douglasii; Spermophilus granimuriis douglasii; 
Spermophilus douglasii; Citellus ieecheyi douglasii; Spermophilus grammurus 
beecheyi, part ; Citellus grammurus douglasii. 

Field characters. — As for the Beechey Ground Squirrel, from which differs notice- 
ably in the possession of a blackish brown wedge-shaped patch on the fore part 
of the back ; also shoulders more extensively silvery white, and tail longer. Length 
of body alone, in males about 11 inches, with tail about 8 inches more. 

Description. — Adults in early summer pelage : Crown of head to nose buckthorn 
brown, becoming mixed with blackish toward eyes and ears ; backs of ears deep bister 
brown margined behind broadly with clay color; insides of ears dull cinnamon-buff; 
eyelids white ; whiskers black ; side of head and of body behind shoulder deep bister 
brown, with much buffy white tippings to hairs ; a conspicuous wedge-shaped patch 
on middle of fore part of back, with apex at nape of neck, solid deep bister brown 
in color, almost black in some specimens ; shoulder patch extensively silvery white, 
this extending backwards to hinder end of median dark wedge. Hinder portion of 
body colored as in the Beechey Ground Squirrel, but dappling more conspicuous, due 
to the whiter tone of the light spots. Under surface of body of darker tone than in 
beecheyi, seemingly due to the darker, sepia brown, bases of the hairs shov/ing 
through the dull white or buffy overwash. Feet as in beecheyi but clouded above with 
dusky. Tail colored as in beecheyi but light tippings to hairs greater in extent and 
Whiter in tone, thus accentuating the white fringe, and producing a grayer effect 
throughout. 

Color variations. — Young but a third grown usually show the characters of the 
species, both as to color and relative tail length, quite as well as do adults.' In one 
example, however, the black dorsal wedge is considerably obscured by buffy mottlings, 
and it thus resembles beecheyi of the same age. 

The effects of wear and fading rarely bring such extreme modification of color tones 
in douglasii as in beecheyi and fisheri, possibly due to the lesser intensity of the 
sunlight and dryness to which their habitat is usually subject. The black wedge on 
the fore back is most vivid in fresh pelage ; in cases where wear and fading have 
progressed to an extreme degree, the black wedge is much dulled toward brown, and 
may be effaced almost entirely. The identity of the ground squirrels in any given 
locality can be determined with certainty by securing several individuals, when the 
normal, distinctive coloration is sure to be shown by some of them. 

Measurements. — Average and extreme measurements, in millimeters, of seventeen 
full-grown specimens from the northwestern counties of California (Sonoma to 
Humboldt) are as follows: Twelve males: total length, 478 (438-504) ; tail vertebrae, 
200 (175-221) ; hind foot, 60 (57-63) ; ear from crown, 23 (19-29) ; greatest length 
of skull, 60.5 (57.8-63.1) ; zygomatic breadth, 37.0 (34.9-38.2) ; interorbital width, 
14.3 (13.5-15.7). Five females: total length, 439 (427-453); tail vertebrae, 192 
(161-210) ; hind foot, 57 (56-60) ; ear from crown, 23 (18-26) ; greatest length of 
skull, 58.5 (56.8-60.4) ; zygomatic breadth, 35.9 (35.0-36.8) ; interorbital width, 14.0 
(13.1-15.0). 

Always taking age into account, there appear to be fairly diagnostic average skull 
characters for douglasii as compared with beecheyi, fisheri and nesioticus. Douglasii 
averages smaller in regard to auditory bullae, and narrower as regards rostrum and 
braincase. Yet, as the above measurements show, the gross size of the skull is not 
especially different. 

Type locality. — Probably somewhere in southern Oregon or northern California. 
The type was a hunter's skin "received from the banks of the Columbia" (Richardson, 
1829, p. 172). 

Distribution area in California. — Roughly, the northwestern section of the 
state, north of San Francisco Bay, west of the lower Sacramento River, and north of 
a diagonal line from near Chico northeast to the Nevada line near the southern 



THE GROUND SQUIRRELS OF CALIFORNIA. 645 

boundary of Modoc County. (See map, fig. 17.) Life-zone, Upper Sonoran aiid 
Transition, ranging down into Lower Sonoran along the western side of the Sacra- 
mento Valley. Altitudinally, the species ranges from near sea level up to as high as 
6,500 feet (near South Yolla Bolly Mountain) and even 6,800 feet (on the Scott 
Mountains, Siskiyou County). 

More in detail : The southern limit of the range of douglasii is not known to reach 
the Golden Gate; it falls, on the sea-coast, somewhere not far to the north of Point 
Reyes Station, and extends from there to the vicinity of Petaluma, leaving the south- 
ern two-thirds of Marin County uninhabited. It extends nearly or quite to Benicia 
and to the southern end of the range of hills west of Vacaville. The flood-plain of 
the Sacramento River forms the eastern boundary north to beyond the Marysville 
Buttes, Thence northeastward, across the Sacramento Valley, there is no obvious 
barrier. In Butte, Plumas and Lassen Counties the ranges of douglasii and beecheyi 
approach very closely, but so far as known they do not overlap ; nor have undoubted 
hybrids or geographic intergrades been reported. 

Specimens examined. — A total of 65, from the following localities in California: 
Modoc County : Sugar Hill, 3 ; Parker Creek, Warner Mts., 3 ; Deep Creek, Warner 
Mts., 1. Siskiyou County : Mayten, 1 ; six miles northwest of Callahan, Scott River 
Valley, 6 ; Summerville, 1 ; Castle Lake, 3. Shasta County : McCloud River, near 
Baird, 7. Tehama County : Mill Creek, 2 miles northeast of Tehama, 4 ; four miles 
south of South Yolla Bolly Mountain, 1. Butte County : four miles southeast of 
Chico, 4 ; Dry Creek, on Oroville-Chico road, 3. Glenn County : Winslow, 4. Yolo 
County : Rumsey, 1. Solano County : three miles west of Vacaville, 2. Humboldt 
County : Eureka, 1 ; Fair Oaks, 2 ; Ferndale, 1 ; Ouddeback, 1. Trinity County : Hay- 
fork, 2 ; Helena, 2. Mendocino County : Sherwood, 3 ; three miles south of Covelo, 1 ; 
six miles north of Willets, 1 ; Mount Sanhedrin, 3. Sonoma County : seven miles west 
of Cazadero, 4. 

The Douglas Ground Squirrel belongs to the group of large, bushy- 
tailed, tall-eared ground squirrels which include the California, Fisher, 
Catalina Island and Rock Squirrels, and in common with the first and 
second of these at least it is often called Digger Squirrel. Although 
the differences are not great, they are evident and should be recognized 
in economic work, for they not only concern color, but apparently also 
habitat and food preferences. The Douglas Squirrel differs from its 
next neighbor of the ''digger" category, the California, in having a 
conspicuous blackish wedge-shaped patch on the middle of the back 
between the shoulders, in having the shoulder region more extensively 
grayish white, and in having the tail a little longer and grayer. 

The name of the squirrel now under discussion was bestowed upon it 
(Richardson, 1829, p. 172) in acknowledgment to an early English 
explorer in western America, David Douglas, for having brought home 
specimens of the animals met with, many of which proved to be new 
to science. Douglas's travels carried him through parts of Oregon 
and probably northern California ; but the type of this ground squirrel 
was a hunter's skin received from the Columbia River. There is no 
telling now exactly where it really came from originally, though prob- 
ably from much south of the Columbia, since the species is not known 
to have existed within history that far north. 

In northern California the Douglas Ground Squirrel occupies a wide 
area ; in fact, at the extreme north from the Pacific Ocean to the Nevada 
line. To the southward its range includes all of the upper Sacramento 
Valley, and its western half lower down, and the whole coast region 
(hills and included valleys) south nearly to San Francisco Bay. Refer- 
ence to the map (fig. 17) will show that the range of the Douglas is 
almost exactly complementary to that of the Beechey; at no point do 



646 THE MONTHLY BULLETIN. 

they overlap, or, indeed, as far as known, quite meet. Roughly, the 
Douglas Ground Squirrel occupies the northern and northwestern third 
of the state. 

The local or habitat preference of this species is more exclusively 
for hilly country than in the case of the California Ground Squirrel. 
It is true that the Douglas exists out on the floor of the Sacramento 
Valley nearly to the lands annually flooded along the river; but it 
occurs there interruptedly, in far separated "colonies," and never any- 
where are the great numbers reached that characterize heecheyi in the 
San Joaquin Valley. The preferred haunts of douglasii are the open- 
ings or glades on hillsides, beneath scattered oaks or pines, or else the 
open tracts along stream courses, not, however, quite down to the 
water's edge. The edges of the smaller valleys between the coast ranges 
are well populated, but the open floors of these valleys are not often 
invaded very far or in any considerable numbers. Dense chaparral 
and thick woods are avoided altogether. 

It is interesting to note here that where the coast redwoods have been 
lumbered out the Douglas Ground Squirrels have come in from the 
interior so as to be plentiful where formerly scarce or wanting. Chapar- 
ral slopes which have been swept by flre are also quickly invaded and 
occupied for a time, until the brush grows up thickly again. It is 
probable that the squirrels are unable to maintain themselves against 
enemies, such as bobcats, that habitually hunt by stealth through under- 
brush ; the squirrels require a certain amount of space around them so 
that they can have a fair show of reaching the safety of their burrows 
after an enemy is first caught sight of. Even though the Douglas 
Ground Squirrels are nowhere so very numerous as compared with 
certain other rodents, their predilection for clearings brings them into 
economic prominence locally. We have been told repeatedly of cases 
where newly cleared farms in mountain valleys have been invaded at 
harvest time from the nearby hillsides, to the almost complete loss 
of the crops. 

It is a curious thing that the Douglas Ground Squirrel should not 
occur south clear to the shores of San Francisco Bay, inasmuch as the 
Beechey on the south side of the bay extends up to either the very 
shore line itself or to the margin of the salt marshes adjacent, or did so 
until very recent years This may be merely another indication of the 
lesser degree of aggressiveness or prolificness on the part of the Doug- 
las Squirrel. Marin County seems to be devoid of any ground squirrels 
whatsoever, except for a few douglasii along the Sonoma County bor- 
der. Joseph Mailliard (interviewed on May 8, 1918) states that in his 
forty years or more of residence in Marin County, he never saw any 
ground squirrels in the southern part or west war dly towards Point 
Reyes. Individuals were seen twice many years ago on the Rancho San 
Geronimo, but ' ' they never stayed. ' ' To all appearances the conditions 
here are identical with those in the Russian River district and a few 
miles west of Petaluma where the animals in question are plentiful, 
or used to be until successfully combated. 

Within the California portion of its range the Douglas Ground Squir- 
rels are believed to be most numerous in Tehama County, this according 
to the consensus of opinion in the office of the State Superintendent of 
Rodent Control. In Shasta County, next on the north, there are rela- 

54 



THE GROUND SQUIRRELS OP CALIFORNIA. 647 

tively few. To the westward they extend within a mile of the seacoast 
in the vicinity of Eureka and at Cape Mendocino, but elsewhere mostly 
not closer to the sea than eight or ten miles. Nowhere in the immediate 
coast belt are they reported especially numerous or injurious. Pocket 
gophers there loom up as the most destructive rodent. 

The voice and mannerisms of the Douglas Ground Squirrel are not 
to us in any points that can be remembered materially different from 
those of the California Ground Squirrel. A fair test of this could, of 
course, only be made upon the two if studied side by side under per- 
fectly normal conditions. In the nature of the case this is impossible, 
for in no known locality do they occupy common ground. 

The tail is at all times the most conspicuous feature of this ground 
squirrel. Sometimes when running to its burrow a squirrel will hold 
its tail in a continuously vertical position, or this member may be 
thrashed fore and aft. Ordinarily the tail is held nearly parallel to 
the ground, with more or less of an arch in it. In this posture of tail 
one is reminded strongly of the Gray Squirrel. 

Our own observations, and the testimony of people in general who 
are familiar with several of our ground squirrels including the Douglas, 
indicate that the latter is the most prone of all to climb trees. For 
instance, near Tehama, June 8, 1912, several individuals were seen 
well up in large white oaks (W. P. Taylor, MS). At Winslow, Glenn 
County, June 19, 1912, one was seen in a buckeye, and several from 
twelve to fifteen feet above the ground in willows and cottonwoods 
(W. P. Taylor, MS). At Sisson, Siskiyou County, August 11, 1914, 
one was seen thirty feet above the ground in an incense cedar (T. I. 
Storer, MS). It is a common thing to see them perched upon the 
tops of fence posts or stumps. Individuals may under certain circum- 
stances so nearly resemble Gray Squirrels as to be actually mistaken 
for them. This emphasis of the tree-climbing habit in the Douglas 
Ground Squirrel is, suggestively enough, thus associated with greater 
length of tail and grayer tone of color of tail, as compared with its 
nearest relatives. It seems, also, that this species, more generally than 
any other, raids orchard trees such as almond and apricot. 

The sure test, on the basis of behavior, of a ground squirrel as com- 
pared with any true tree squirrel, such as the California Gray, is that 
the former, no matter how high in a tree when discovered, will, upon 
alarm, take to the ground as cjuickly as possible, and seek safety in a 
burrow below ground, rather than make off through the branches from 
tree to tree, or ascend into the uppermost foliage of a treetop. Not 
infrequently, when surprised in a tree, a ground squirrel will for the 
time being ''freeze" and attempt to escape being seen by remaining 
motionless. But after being further disturbed and once starting, he 
makes for the ground by the shortest route. 

The burrowing habits of the Douglas Squirrel are similar to those 
of related species. Steep banks seem to be chosen for burrowing into, 
whenever available. Many burrows open under rocks, bushes and 
tree roots. On open, level ground, with no protective shelter at hand, 
the mouths of the burrows are niarke.d by good-sized mounds, showing 
the presence of an extensive system below ground. As far as we know, 
no one has yet made a complete excavation of the burrow system of 
this species. 



648 THE MONTHLY BULLETIN. 

The breeding season is indicated by the time of appearance of the 
young aboveground. In Scott Valley, Siskiyou County, where the 
species is abundant, very small young were seen abroad on June 8 
(1911). At Winslow, Glenn County, young one-fourth to one-half 
grown were captured on June 16 (1912). At 6,800 feet altitude on the 
Saloon Creek Divide, in the Scott Mountains, Siskiyou County, July 
10 (1911), nursing females were captured, but no young were yet out 
(L. Kellogg, MS). It is thus probable that at the lower altitudes the 
young are born during the last half of May, while at the highest levels 
they are not born until at least a month later. Only one litter is reared 
each year. 

Unfortunately we have no facts of our own to offer in regard to 
size of litter. We have an idea that fewer young are born each year 
than in the case of the California Ground Squirrel, judging roughly 
from the numbers of young seen aboveground, about five. But this is 
almost pure conjecture. F. E. Garlough, of the Uniled States Bio- 
logical Survey, is under the impression (interviewed September 7, 
1918) that litters in the lowlands average close to eight, while, in. the 
mountains five is the usual number. He has known of as few as two 
and as many as fourteen embryos having been found in pregnant 
females. 

The following definite data on file in the Museum of Vertebrate 
Zoology show some of the kinds of food selected by the Douglas Ground 
Squirrel and also the quantity in which each of these kinds may be 
gathered at one time. A male squirrel taken on Dry Creek where 
.crossed by the Oroville-Chico road, in Butte County, May 31, 1912, 
contained in its cheek pouches 29 seeds of a wild lupine {Lupinus 
micranthus) . Three others taken on Butte Creek, near Chico, June 3 
and 5, 1912, contained in their cheek pouches materials as follows: 
male, 12 seeds of milk thistle (Silyhum marianum) ; female, 219 grains 
of barley and one head of English plantain {Plantago lanceolata) ; 
female, 142 grains of barley. The cheek-pouch contents of two squirrels 
taken on Mill Creek, near Tehama, June 12, 1912, consisted of, respec- 
tively : female, 121 seeds of bur clover {Medicago hispida) and 70 small 
unidentified seeds, part loose and part in three whole pods ; female, 181 
seeds of brome-grass (Bromus carinatus) and one piece of an acorn. 
Two squirrels taken in the hills three miles west of Vacaville, July 3 
and 6, 1912, contained in their cheek-pouches : female, 29 seeds of Napa 
thistle (Centaurea meUtensis) and 30 seeds of bur clover; male, 82 
seeds of bur clover, 4 seeds of Napa thistle and one cherry pit. A 
male taken three miles south of Covelo, Mendocino County, July 20, 
1913, held in its cheek-pouches 14 whole fruits and 103 separate seeds 
of the common manzanita {Arctostaphylos mmizanita), as also a few 
small unidentified seeds of two kinds. 

From all sources comes the testimony that this species takes barley 
and wheat with particular avidity. Its storage propensities are highly 
developed, and it would be interesting to see actual figures as to the 
quantity of grain garnered underground in one autumn season. Where 
they invade apricot orchards, as in the foothill district of the Warner 
Mountains near Alturas, these squirrels climb the trees and take out 
the pits, discarding the pulp of the fruit. 



THE GROUND SQUIRRELS OP CALIFORNIA. 649 

The Douglas, as is known of most other ground squirrels, is fond of 
flesh when this can be obtained. Many have been taken in the meat- 
baited steel traps kept out in various localities for carnivores. 

Hibernation seems to be more prevalent with douglasii than with 
teecheyi, for all of the population of the former is reported to disappear 
for weeks at a time, even in the lower valleys. At the higher altitudes, 
where there is more or less heavy snow, all the squirrels disappear over 
a period of some months. In Hayfork Valley, Trinity County, the 
senior author was assured by several different people living there that 
the Douglas Squirrels hibernate regularly and completely "from Novem- 
ber till April." The earliest spring record we have for a mountainous 
region is of one squirrel caught in a box trap February 25 (1911) near 
Helena, Trinity County (A. M. Alexander, MS). 

The natural enemies of this squirrel probably include practically all 
those already specified in our chapter on the California Ground Squir- 
rel. Only one specific instance is at hand. A gopher snake found 
run over in a road near Chico, June 7, 1912, was found to contain in its 
stomach a young Douglas Ground Squirrel (T. I. Storer, MS). 
Coyotes are locally reputed to levy considerable toll upon this rodent. 
We have heard the argument advanced against the poisoning of ground 
squirrels on wild mountain land in the northwest coast district that 
reducing the squirrel population will deprive the coyote of one of his 
chief sources of subsistence and that he will thereupon be forced to 
seek food elsewhere and so be more prone to raid the poultry of the 
valley ranches and the flocks of sheep in the mountains. On the other 
hand, it may be advanced that the total coyote population is adjusted 
to the total amount of food available at the season of least supply, and 
that removal of any one important kind of food will in course of time 
reduce the total coyote population able to exist in any general territory. 

A high natural mortality for this species may account for its relative 
lack of aggressiveness as compared with the California Ground Squirrel. 
The testimony of a number of people from localities widely scattered 
over the range of the Douglas Ground Squirrel is to the effect that 
every few years there is a great reduction in its numbers. Some fairly 
close observers, forest rangers in the Trinity region, for instance, think 
this is due to the effects of severe winter weather, as when there is an 
exceptionally heavy snowfall or torrential rains of unusual amount. 
In either case the squirrels are thought to be drowned in large propor- 
tion when lying dormant underground. Other persons think there are 
recurrent epidemics of some disease fatal to the ground squirrels. We 
have no-good evidence bearing upon either hypothesis. 

Because of this observed reduction in numbers during some winters, 
certain ranchers have objected to carrying on poisoning operations in 
the fall, since their efforts might prove to have been unnecessary. 
They prefer to. deal with the naturally reduced squirrel population of 
the springtime, at the close of the dormant period. 

The general range of the Douglas Ground Squirrel has not changed 
within history as far as definite records show. But, locally, there have 
been marked fluctuations. On the western side of the Sacramento 
Valley the animals have been almost completely cleaned out on many 
large tracts as a result of systematic poisoning. This is particularly 
true, as we are assured by W. C. Jacobsen, State Superintendent of 

57 



650 THE MONTHLY BULLETIN. 

Rodent Control, of the Davis, Williams, Willows and Orland districts. 
The reason for this is twofold: The Douglas Squirrels never did have 
a secure foothold in the Sacramento Valley, such as the Beechey Squir- 
rels have in the San Joaquin Valley; and the former, according to 
current impression, takes the poisoned grain more readily. 

On the other hand, with the clearing of forest lands in the coast dis- 
trict, through lumbering and homesteading, the squirrels are thought 
to have extended their confines locally. At any rate, they have become 
numerous where formerly absent altogether or present in such small 
numbers as to have been overlooked by the average person. 

In certain sequestered valleys among the northern coast ranges we 
have been assured of a loss to grain crops, where no effort at poisoning 
the squirrels had been made, of from 5 to 25 per cent. In such cases 
the squirrel population from the wild land immediately adjacent seemed 
to have moved in en masse, as harvest time approached, to take advan- 
tage of the special food supply thus made available. Nevertheless, the 
Douglas Ground Squirrel, by reason of its relatively sparse population 
over most of its range, and the ease with which it can be reduced in 
numbers with reasonable effort, does not rank as of so much economic 
importance as some other species. We would place it fourth among 
our ground squirrels, giving precedence to the California, Oregon 
and Fisher. 



ROCK SQUIRREL. 
Citellus variegatus grammurus (Say). 



other names. — Plateau Ground Squirrel ; Rocky Mountain Ground Squirrel ; 
Citellus grammurus. 

Field characters. — As for the Beechey Ground Squirrel, differing in longer tail and 
grayer general coloration ; fore parts of body continuously grayish white, without 
specially set-off shoulder patches. Length of body alone about 10^ inches, with tail 
about 8 inches more. 

Description. — Summer pelage: Head dull buckthorn brown, grizzled on cheeks and 
sides of snout ; eyelids dull white ; whiskers black ; backs of ears dull buffy brown, 
insides of ears pinkish buff. Forward half of upper surface of body light gray, with 
decided dusky mottling in transverse trend ; hinder half of upper surface, of a tawny- 
olive tone, lighter on sides, and with similar transverse mottling. Whole lower surface 
of body and upper surfaces of feet, pale pinkish buff, nearly white in some specimens ; 
belly with grayish bases of hairs showing through. Tail considerably bushier than in 
beecheyi, as well as being longer; length of hairs up to 50 mm. (2 inches) ; tips 
of hairs more extensively white, thus nearly as in douglasii; dark and light intervals 
on individual hairs same as in heecheyi, that is, three dark and four light, the latter 
including the tipping. 

Color variations. — Wear and exposure to intense sunshine evidently accounts for 
the yellowing of the pelage of one specimen at hand ; also the tail of the animal shows 
a curious crinkling of the hairs as if scorched. An adult of date June 2 has the 
forward half of the body in fresh new (summer) pelage ; this is relatively harsh in 
texture, without underfur. Young less than half grown are colored almost exactly as 
described above for adults, but the pelage on the under surface is very scanty, so 
that the bare skin shows through extensively. No winter specimens are at hand from 
within the state of California. 

Measurements. — Only two adult specimens are available from California. These 
are from the Providence Mountains, eastern San Bernardino County, and show meas- 

58 



THE GROUND SQUIRRELS OP CALIFORNIA. 651 

urements, in millimeters, as follows : Male and female (nos. 117301 and 117300, 
respect'vely, Biol. Surv. coll., U. S. Nat. Mus.) : Total length, 470, 465 ; tail vertebrae, 
194, 205 ; hind foot, 58, 54 ; ear from crown, 20, 21 ; greatest length of skull, 61.2, 
58.4; zygomatic breadth, 38.5, 37.0; interorbital width, 15.4, 14.2. 

No skull differences of ciucial importance between grammurus and ieecheyi are 
apparent to us in the material at hand for study. 

Type locality. — Purgatory River, near mouth of Chacuaco Creek, Las Animas 
County, Colorado (according to Cary, 1911, p. 87). This form was originally 
described by Thomas Say in 1823. 

Distribution (in California). — Inhabits the Providence Mountains, in eastern San 
Bernardino County (see fig. 17) ; also "the canyons of the Colorado River" (Merriam, 
1910, p. 2). Life-zone chiefly Upper Sonoran, 

Specimens examined from California. — A total of five, all collected by Frank 
Stephens, June 1 to 3, 1902, in the Providence Mountains, 5,000 to 5,500 feet alti- 
tude. These were loaned us from the Biological Survey collection, United States 
National Museum. 

The Rock Squirrel is really a very close relative of the Beechey 
Ground Squirrel and its habits are doubtless closely similar. It is a 
wide-ranging form through the southern Rocky Mountain region, sta- 
tions of occurrence in southeastern California being merely far western 
outposts. Two of the specimens from the Providence Mountains are 
young less than half grown; these were taken on June 1, and indicate 
a breeding date at about the same time of year as for other ground 
squirrels in the upper Sonoran zone. 



OREGON GROUND SQUIRREL. 
Citellus oregonus (Merriam). 



PLATE II. 



other names. — Oregon Spermophile ; Bull Dog ; Prairie Dog, part; Gopher; Bobby ; 
Sand Rat ; Short-tail ; Woodchuck ; Belding Ground Squirrel, part ; Picket-pin, part ; 
Spermophilus oregonus; Citellus ieldingi, part; Spermophilus richardsoni. 

Field characters. — A medium sized, short-tailed ground squirrel, of stocky build, 
and of brownish gray coloration without special stripes or markings of any sort (see 
fig. 20a). Length of body alone about 8i inches, with tail about 2i inches more. 

Description. — Adult in slightly worn spring pelage : Whole upper surface of a 
general drab tone of coloration, tinged with cream-buff along sides and with dull 
cinnamon on top of head and down middle of back. There is usually a faint pattern 
of fine dappling. Eyelids dull white ; whiskers black ; ears clothed with short hairs, 
like top of head in color. Upper surfaces of feet tinged with warm buff ; palms naked ; 
soles naked except for sparse hairing forward from heel nearly to tubercles ; claws 
horn-color, dusky at bases. Tail full-haired, flattish, widest about one-fourth way 
back from end ; color on upper surface mostly like back, except for showing through 
of the hazel bases of the hairs, and for black zone about end succeeded by a 
buffy white fringe ; under surface of tail bright cinnamon rufous, with a broad band 
of black at end and continuing backwards a little ways along either side, and the 
whole margined narrowly with buffy white. Under surface of body dull cream-buff, 
paling on throat and inner sides of legs ; much brownish lead-color of the hair-bases 
shows through on abdomen. 

Color variations. — As wear proceeds toward an extreme the whole coat becomes 
grayer, and the cream-buff tints tend to disappear by fading. Males usually remain 
much less worn than females ; otherwise we can see no differences in coloration 
between the sexes. The material we have shows evidence of but one molt each year. 



652 THE MONTHLY BULLETIN. 

this beginning about July 1st; but we have no specimens of dates between August 
and May. It is possible that there is an autumn molt leading into a distinct winter 
coat. Small young are softer-pelaged than adults, but colored just the same. 

Measurements. — Average and extreme measurements, in millimeters, of nineteen 
mature specimens from northeastern California are as follows : Nine males : total 
length, 275 (260-300) ; tail vertebrae, 65 (56-80) ; hind foot, 42 (37-45) ; ear 
from crown, 9 (7-11) ; greatest length of skull, 45.1 (44.2r-46.5) ; zygomatic breadth, 
29.1 (27.1-31.0) ; interorbital width. 10.4 (10.0-11.1). Ten females: total length, 
280 (271-292) ; tail vertebrae, 57 (47-68) ; hind foot, 43 (41-44) ; ear from crown, 
7.5 (6-8) ; greatest length of skull, 45.7 (44.9^7.2) ; zygomatic breadth, 29.7 
(29.1-30.4) ; interorbital width, 10.4 (9.7-10.9). 

From the above figures it would seem that, in this ground squirrel, females are 
larger than males, except for tail and ear. There are chances, however, that measure- 
ment of greater numbers would give somewhat different results. It must be kept in 
mind that the figures taken from the freshly killed animals were supplied by 
several different people, and method of securing each measurement undoubtedly varies 
somewhat with the persons doing the measuring. Even with the skulls, all measured 
by the senior author of this paper, size clearly varies to some degree with age, and the 
proportions present in our series, of animals of different ages, will naturally affect 
the average. 

Weights. — Average and extreme weights, in grams, of six full grown females are: 
302 (267-365.8). This average in ounces is about 10^. The heaviest example was 
notably fat, the lightest, lean. Adipose tissue thus counts importantly in weight, 
though probably also weight increases, as does size of skull, with age. The animals 
would probably weigh most just prior to hibernation, as they are then fattest. 

Type locality. — Swan Lake Valley, Klamath Basin [Klamath County], Oregon 
(Merriam, 1898, p. 69). 

Distribution (in California). — Occupies the northeastern corner of the state, 
comprising the counties of Modoc, Lassen, eastern Siskiyou, and a portion of Plumas 
(see fig. 18). The metropolis of the species lies in the Upper Sonoran life-zone, but 
the animals extend through Transition, and even enter the Canadian. In detail : 
west from the Nevada line as far as the vicinity of Goose Nest Mountain, Siskiyou 
County, and vicinity of Big Meadows, in extreme northern Plumas County ; south 
from the Oregon line to the last named locality and to the valley of Susan Creek, 
in Lassen County. Altitudinally, this ground squirrel extends from as low as 3,300 
feet, on the Pit River, up to 9,000 feet, on Warren Peak, Warner Mountains (Mus. 
Vert. Zool.). 

Specimens examined. — A total of 51 from the following localities in California: 
Modoc County : Sugar Hill, 4 ; Goose Lake near Davis Creek, 2 ; South Fork Pit 
River near Alturas, 3; Warner Mts. (Parker Creek and Squaw Peak), 6. Siskiyou 
County : near head of Little Shasta River, north of Goose Nest Mt., 1 ; Bull Meadow, 
northeast of Goose Nest Mt., 1 ; seven miles south of Macdoel, 24 ; Grass Lake, 6. 
Lassen County : Termo, 1 ; west end of Horse Lake, 1 ; fifteen miles V7est of West- 
wood, 1. Plumas County : ten miles west of Big Meadows, 1. 

The Oregon Ground Squirrel occurs in California only in the extreme 
northeastern counties of the state; but it has a rather wide general 
range which includes much of Oregon east of the Cascades, and parts of 
northern Nevada. It is a Great Basin plateau species, and its range 
ends to the westward in California rather abruptly in the vicinity of 
Goose Nest Mountain (head of Little Shasta River and Grass Lake) 
and in the Pit River Valley in the vicinity of Burney, Shasta County. 
To the southward it extends to Big ]\Ieadows, in Plumas County a 
little southeast of Mount Lassen, and to the valley of Susan River, in 
Lassen County. 

In most of the sagebrush territory thus bounded, the Oregon Ground 
Squirrel is conspicuously abundant, more so, some people believe, than 
any other species anywhere in this state. "While not so large as the 



THE GROUND SQUIRRELS OP CALIFORNIA. 



6S3 




Fig. 18. Map showing California distribution of tlie Oregon, Belding, Stephens 
Soft-haired, Mohave, Yuma Round-tailed, Death Valley Round-tailed and Palm Springs 
Round-tailed ground squirrels. The spots represent localities from which actual speci- 
mens have been examined. 



Beechey Ground Squirrel individually, it exceeds that species in num- 
bers. At any rate, it ranks highest in importance among rodent pests 
within its domain. 

The Oregon Ground Squirrel is an inhabitant chiefly of mountain 
meadows and the borders of the bigger meadows of the valleys. It 
does not care for marshy ground, and it avoids thick brush and rocky 
slopes. In a way, it is complementary in habitat to the Douglas Ground 
Squirrel, which occurs in much of the same territory; rarely are the 
two seen on common ground. It is obviously because of its preference 
for grass land that the Oregon Ground Squirrel has come so seriously 



654 THE MONTHLY BULLETIN. 

into conflict with man's interests. Extensive clearing of the sage- 
brush and seeding of these clearings to grain and hay has doubtless 
benefited the squirrels. Indeed, this is likely one of the factors that 
accounts for their increase of late years as testified to by several of 
the old-time residents whom we have interviewed. 

In Butte Valley, Siskiyou County, the Oregon Ground Squirrels 
are popularly known as "bull dogs," in Modoc County as ''short-tails" 
(evidently as distinguished from the longer tailed Douglas Ground 
Squirrel), and elsewhere, locally, as "bobbies," "prairie dogs," 
"gophers," and "woodchucks." The last three names, of course, are 
misapplications of names properly belonging to quite different kinds of 
rodents. 

In the latter part of May, 1918, the senior author accompanied Mr. 
W. C. Jacobsen, State Superintendent of Eodent Control, in a tour 
through northeastern California for the particular purpose of studying 
the Oregon Ground Squirrel. In traveling eastward from Shasta 
Valley, we first encountered this species toward the head of the Little 
Shasta River, on the Mills ranch at about 4,200 feet altitude. Here 
we found a field of vetch to be riddled with the burrows and secured one 
of the animals to verify this, the westernmost record station for the 
species. At Bull Meadows, a little east of Goose Nest Mountain, the 
squirrels were exceedingly numerous on the uncultivated open ground 
among scattering lodgepole pines. Subsequently we found them plen- 
tiful around the margins of Grass Lake, nearly as far west, but due 
south of Goose Nest. But it was on the floor of Butte Valley, from 
the vicinity of Bray north to Dorris, wherever there were open grass 
lands, that the Oregon Ground Squirrels simply swarmed. The fol- 
lowing observations made May 16, 1918, on a ranch seven miles south 
of Macdoel, will give an idea of the abundance of the animals where 
conditions are most favorable to them. 

Taking a position at the right-angled intersection of two fences, 
the observer counted the animals in the quarter-circle gaze thus 
bounded and found that there were sixty-five squirrels in plain sight 
within a distance of one hundred yards of him. This was about nine 
o'clock in the forenoon of a bright day, when the squirrels were at 
about the height of their daily activity aboveground. Young of the 
year were included. 

Again, three adjacent plots of pasture were paced off, thirty-nine 
paces square, and the open burrows counted. In one plot there were 
151, in the second 182, in the third 194, an average of 176. This, fig- 
ured out, makes 560 open burrows to the acre! If we allot one adult 
squirrel to each five openings, which our observations showed to be 
about the proper ratio, there would be 112 adults to the acre, not 
counting young. Figuring, further, this would make somewhat over 
70,000 squirrels per square mile ! This, however, would pertain only 
in limited areas and to those pasture lands where little effort had yet 
been, made to reduce the pests. The population of the sagebrush 
plains and pine woods of Butte Valley would be much smaller. It is, 
of course, the pasture lands and grainfields where the squirrels come 
into chief conflict with man's interests, and this is where they are most 
abundant. Some further estimates in this connection are likely to 
prove worth while. 



THE GROUND SQUIRRELS OP CALIFORNIA. 655 

The average weight of six adult female Oregon Ground Squirrels 
was found to be 302 grams (about 10^ ounces). The full stomachs of 
these six squirrels were found to give an average weight of 18.5 grams. 
Subtracting the ascertained weight of the stomach itself (3.5 grams), 
gives the weight of the contents, alone, representing doubtless one full 
meal, as 15 grams, or one-twentieth the entire weight of the animal. 
The stomach contents was in all cases a closely packed, slightly moist 
(not watery) mass of finely chewed green stuff. This could not be 
analyzed as to kinds of plants represented, but the squirrels were seen 
to be feeding upon all sorts of vegetation, practically everything going 
to make up the usual forage grazed from such lands by live stock. 

Our observations led us to believe that, at the very least, two full 
stomach-loads of greens were eaten by each squirrel each day, or 30 
grams of forage. Of course this does not account for wastage, evidence 
of which, in the way of cut stems and grass blades, was plentiful. 
Figuring from the average number of adult squirrels per square mile, 
70,000, and counting on two meals per day, we find a minimum of 
2,100,000 grams, or somewhat more than two tons, of green forage 
devoured by the squirrels each day on a square mile of pasture. 
Granted that a grazing steer eats fifty pounds of pasture forage each 
day, we conclude that the squirrels on a square mile of pasture 
appropriate each day the forage which might support ninety head of 
cattle. 

Expressing it in other ways, 750 Oregon Ground Squirrels during the 
growing season of pasture grass eat as much as one steer, and the 
squirrels on every seven acres of pasture thickly inhabited by them 
eat as much as one steer! 

The burrows of the Oregon Ground Squirrel where the animals are 
at all numerous fairly riddle the ground. Most of the openings come 
to the surface at a rather steep angle and without any earth at their 
mouths. Now and then there is an opening which slants to the surface 
and has a good-sized mound, and such as these seem to mark the 
nesting burrows as distinguished from the short, temporary, refuge 
burrows, or those occupied by males. We spent the entire day of 
May 16 excavating one nesting burrow, with results shown in figure 19. 

The mound at the main entrance to this burrow system was rather 
large in extent, though shallow. It consisted of this year 's loosely piled 
earth, covering up the grass on an area of nearly two square yards and 
thus marking the place conspicuously. The system of burrows, in part 
at least, probably represented two seasons' work and maybe more. 
"While there were only two openings to this system, there were several 
points at which underground branches came nearly to the surface so 
that a hard-pressed squirrel, pursued by some underground enemy, 
could have quickly dug clear out and escaped overland. 

As usual with ground squirrels, the runways were everywhere smooth 
and free from excrement, the nest chamber in use being unexpectedly 
clean. The feces of the young are evidently collected by the mother and 
carried to the places where her own are deposited, in the special 
branches or defecatoria. Here the earth is tamped over the mass in 
such a way that the pellets are kept separated by the soil particles, with 
no chance to fester. The fecal pellets are dryish, anyway. Some 
saved for examination, probably from the adult squirrel, prove to be 




Pig. 19. Plot of a used nesting burrow of the Oregon Ground 
Squirrel, as excavated by J. Grinnell and W. C. Jacobsen in a pasture 
near Macdoel, in Butte Valley, Siskiyou County, May 16, 1918. 

Main opening of burrow-system at a, with shallow, bean-shaped 
mound nearly two square yards in extent opposite. Greatest depth 
of earth in mound, 100 millimeters. Only other opening, at s, flush 
with surface, and without any out-pushed earth. Mouth of burrow 
at a, 100 millimeters wide by 90 high. Mouth of opening at s, 75 by 
60. Dimensions of burrow at f, 75 by 60 mm. ; at c, 90 by 65 ; at d, 
60 by 60; at o, 60 by 60. Depth of burrow at h, beneath surface of 
ground, 300 mm.; at c, 350; at d, 200; at f, 300; at g, 520; at h, 
590; at j, 750; at k, 1,000; at o, 660; at p, 520; at r, 550. Branches 
at i, e and t came nearly to surface of ground. Old nest cavity at fc, 300 mm. in 
diameter, and floored with a damp mixed mass of old frazzled grasses, excrement, 
and earth. At m and Z, chambers, 770 and 1,110 mm., respectively, beneath surface 
of ground, packed full of a mixture of excremental pellets and loose earth. Blind 
terminal at n, 850 mm. deep. New nest, in use, containing many live fleas, at g; 
cavity of this, 190 mm. wide by 170 high, and 700 mm. beneath surface of ground, 
nearly filled with a dry clean hollow mass of shredded juniper bark and weathered 
grasses. The excavating was begun at a, and the female and six third-grown 
young were overtaken at s and t, where they were about to escape. 

Total length of this .burrow system, 66 feet. Average diameter of burrow, 2i 

inches. Volumetric content of entire system, 3i cubic feet. Greatest depth reached, 

45 inches, or nearly 4 feet. 

short-cylindrical or elliptical in shape, and measure 6.5 millimeters 
in diameter by from 15 to 22 in length. 

There were two nest cavities in the system unearthed, an old one, 
and the one in use. The latter contained a dry, hollow mass of frazzled 
juniper bark and weathered stems and blades of grass. The female 
parent and six third-grown young were overtaken farther along in the 
burrow system, near one terminus of it, but that the nest had but 
recently been vacated was shown by its feeling of warmth to the touch 
and the presence of numerous lively fleas. The female proved a tartar 
in defense of herself and young, biting effectively with her sharp incisor 
teeth and scratching with her strong claws. This was as a final recourse, 
however, as the first endeavor on the part of all the occupants, when 
the burrow was opened up, was to escape and run to the nearest shelter, 
such as offered by some neighboring burrow, or by a flat rock. As far 
as our observations went, there was no indication that the adult male 
lives in the same burrow with the female, or has, indeed, anything to 
do with the rearing of the young. 

The burrow system in question was found to be QQ feet long, melud- 
ing the various windings and all of its branches. Its average diameter 
was about 2^ inches, and the volume, or cubical air content, 3| cubic 



THE GROUND SQUIRRELS OF CALIFORNIA. 657 

feet. The greatest depth reached beneath the surface of the ground was 
45 inches. This was in rather dry pasture, and there was no sign of 
a water-table ; the soil to this depth was only moderately damp. 

The notes of the Oregon Ground Squirrel are of two sorts. The 
most impressive consists of a series of from 8 to 12 shrill, high-pitched 
calls, uttered in rapid succession — seep, seep, seep, seep, seep, seep, seep, 
seep, seep. The tendency is to weaken on the last few syllables, but 
the same pitch is nearly or quite maintained throughout. This call 
seems to be uttered only by adults, and seems to signify alarm at the 
first, or distant, approach of danger. One hears it taken up here and 
there all over a large meadow when it is first entered. Then there is a 
single shrill chirp of somewhat lower pitch, uttered now and then by 
either old or young. At times one will hear scarcely a note for many 
minutes, even when many of the squirrels are in sight, and then again 
the calls will be given back and forth from all sides. 

One old female watched from a distance of 20 feet stood stock still 
for several minutes at the mouth of her burrow, in upright, "picket- 
pin" fashion. The fore feet she held against her stomach in front. 
When she gave the several syllabled call she opened her mouth very 
wide, depressing the tongue on to the floor of her mouth so that it could 
not be seen, and uttered the successive notes with much appearance of 
effort. The convulsive movements of the body were synchronous with 
the notes as uttered. The picket-pin attitude is really not so frequent 
as a crouching one, though when it is assumed it renders the squirrel 
visible a long way, especially where the grass is short. When feeding, 
the squirrel hunches over on its haunches, and uses both front feet and 
the fingers of these for holding and manipulating the food. When 
foraging the squirrels do much slinking along, with body horizontal and 
seemingly touching the ground. When a general alarm is sounded one 
sees them running in every direction, with a rather clumsy and not 
rapid, hopping gait. When so running the tail, short and never con- 
spicuous, is held either out straight behind or raised at an angle 
of 30 degrees. Often when halting, or coming to a stand on the alert, 
the tail is twitched up from the horizontal several times in rapid 
succession, the whole body also twitching at the same time. 

Rarely does an Oregon Ground Squirrel leave the ground, even to 
climb onto a rock or log. The body is relatively heavy and the general 
movements are far from nimble. In just one instance was a squirrel 
observed to have actually climbed; one individual was seen at Sugar 
Hill, Modoc County, up in a bush four feet above the ground (W. P. 
Taylor, MS). Marshes or very wet meadows are avoided; in other 
words, this species does not take to water. Still, we have the one 
instance of an individual, near Oanby, Modoc County, seen (W. C. 
Jacobsen, MS) swimming across the Pit River. The current here was 
sluggish and the channel about eighteen feet wide. The act was to 'all 
appearances voluntary. 

At the season of our special observations, the middle of May, the 
Oregon Ground Squirrels were seen to be feeding on practically every 
sort of pasture vegetation. Cuttings of meadow grass, blades and stems 
of grain, and leaves and stems of alfalfa were seen on their mounds or 
in the mouths of their burrows. As already stated, determination of 



5-43C07 



658 THE MONTHLY BULLETIN. 

the kinds of plants eaten, from stomach examination, proved impractica- 
ble because the food is chewed so finely. Even young less than a third 
grown were feeding freely on green stuff. Six young taken on May 16 
were found to weigh from 65.1 to 104.7 grams, averaging 82.4 grams as 
compared with 302 grams, the average weight of adults. Their stomachs 
were distended with finely cut food, and were found to weigh on an 
average 5.4 grams, or about one-fifteenth their total weight as against 
the one-to-twenty ratio in adults. It would seem that partly grown 
young eat more in proportion to their size than old squirrels — which was 
rather to be expected. 

There seem to be two periods of maximum daily activity above- 
ground on clear days, about 9 a.m. and again in mid-afternoon. This 
squirrel seems to be preeminently a sunshine forager. One day when 
a thunderstorm came up in the afternoon the squirrels nearly all dis- 
appeared from aboveground coincidently with the gathering of the 
clouds. 

The breeding season of the Oregon Ground Squirrel, as is to be 
expected, varies with altitude, or, rather, with life-zone. The young are 
born later in the Transition and Boreal zones, than in the Upper 
Sonoran. On May 15 scores of adults were seen on Bull Meadows, near 
Goose Nest Mountain, 5,000 feet altitude, in the Canadian zone, but not 
one youngster was seen; while on May 16 everywhere in Butte Valley 
around Macdoel, at 3,000 feet, in the Upper Sonoran zone, young were 
out in great numbers. All of these were of about the same size, one- 
fourth to one-third grown, showing the uniformity of time of birth 
throughout a region of uniform temperature conditions. On May 19, 
1910, a collecting party from the California Museum of Vertebrate 
Zoology found small young, just out, on Sugar Hill, 5,000 feet altitude, 
Modoc County. 

There is but one litter a year, and the number to a litter is supposed 
to vary from 4 to 15, averaging about 8. Exact statistics from which to 
determine these figures accurately are not available. A man who was 
irrigating an alfalfa field near Macdoel regularly day after day told us 
that he had drowned out many families of young and that the broods he 
had seen consisted of from 4 to 11, averaging, he thought, 8. Mr. W. C. 
Jacobsen, from his own extensive experience with this species, considers 
4 and 12 to be extremes, and 8 the average. He knows, indirectly, of 
one case of 15. 

The Oregon Ground Squirrels lie dormant in a dry nest beneath the 
surface of the ground for fully half the year, even at the lowest altitudes 
in the general territory inhabited by them. The bulk of the population 
goes into hibernation during July and does not come out until March. 
These statements are made upon the authority of Mr. W. C. Jacobsen, 
who is further of the opinion that the exact time of disappearance, which 
varies somewhat from year to year, is controlled by moisture and conse- 
quent supply of green food. The drier the year the earlier the squirrels 
go into winter quarters, this in spite of the hotter late-summer tempera- 
ture at the lower altitudes. In 1915, the squirrels in Big Valley, Lassen 
County, had nearly all gone in by July 3; in Warm Springs Valley, 
Modoc County, they had gone in by July 10 ; but on the Warner Moun- 
tains, Modoc County, they were just going in on July 22 of the same 
year. In 1914, a year of more moisture and better feed, the time of 



THE GROUND SQUIRRELS OP CALIFORNIA. 659 

beginning hibernation at the same points was one and one-half to two 
weeks later. Individuals have been reported to us as seen aboveground 
as late as the first week of September, but all reports agree that the 
majority are "holed up" before the first week in August. 

In the spring the animals reappear often when there is yet much 
snow on the ground. In 1916 they were out in force on March 16, when 
they had burrowed up in places through two feet of snow and were 
nibbling the sagebrush tips (W. C. Jacobsen, MS). 

Enemies of the Oregon Ground Squirrel were, under original condi- 
tions, doubtless numerous and effective in keeping down its numbers. 
Gopher snakes, rattlesnakes, badgers, coyotes and Swainson Hawks are 
known to feed regularly on it. Mr. J. O. Miller, a professional trapper 
living at Yreka, informs us that nine out of ten coyotes trapped by him 
during the summer months have remains of ground squirrels in their 
stomachs. One coyote taken in Butte Valley had parts of seven Oregon 
Ground Squirrels in its stomach. An old-time resident near Alturas 
told the senior author that the killing off of the "varmints" (predaeeous 
animals) in recent years seemed to him to have had something to do 
with the increase and spread of ground squirrels. We are strongly 
inclined to his belief. Encouragement of those natural enemies which 
are not in themselves seriously detrimental to man's interests would go 
far to check the undue increase of the ground squirrels. 



BELDING GROUND SQUIRREL. 
Citellus beldingi (Merriam), 

PLATE III. 

Other names. — ^Belding Spermophile ; Bob-tailed Spermophile ; Prairie Dog, part; 
Picket-pin, part; Spermophilus elegans ; Spermopliilus ieldingi; Colobotis beldingi. 

Field characters. — A medium-sized, short-tailed, "picket-pin" type of ground 
squirrel, without side-stripes or other conspicuous markings, but with bright reddish 
brown back. Length of body alone about 7f inches, with tail 2| inches more. 
(Closely similar to Oregon Ground Squirrel, but smaller and with back reddish 
brown instead of brownish gray; compare figs. 20a and 20b.) 

Description. — Adult in full fall pelage : Sides of head, hind neck, shoulders, sides 
of body and flanks continuously yellowish brown (numerous fine hairs which are 
chiefly black, though light-tipped, lend a dusky tone to these areas) ; a tinge of olive- 
ochre pervades the lower margins of those areas adjoining the light underparts ; eyelids 
white; whiskers black; ears dusky, finely haired, not tufted; crown of head to nose, 
tawny-olive; a broad sharply outlined band of bright hazel brown running down 
middle of back from between shoulders, narrowing to base of tail. Tail short, full- 
haired, flatfish ; above mixed hazel and black, black predominating toward end, where 
also a well-defined buffy white fringe ; under surface of tail conspicuously deep 
cinnamon-rufous, with subterminal black interval, and buffy white fringe all around. 
Upper sides of feet buffy white ; claws chiefly black, with horn-colored tips ; palms 
naked ; soles naked save for sparse hairing from heel halfway to tubercles. Under 
side of head and neck, and inner sides of fore and hind legs, buffy white ; belly 
cream-color, with lead-color of bases of hairs showing through. 

Color -variations. — As far as we can see from the series of specimens studied, 
adults molt but once a year, during July. May and June specimens show clearly 
the effects of wear and fading, and are grayer, with the mid-dorsal brown area much 
duller than in the fresh pelage described above. Young not one-fourth grown are like 
adults in color, but with mid-dorsal area paler, snuff brown, and under side of tail clay 
color. 

67 



660 THE MONTHLY BULLETIN. 

Measurements. — Average and extreme measurements, in millimeters, of twenty 
mature specimens from the Yosemite section of the high Sierra Nevada are as 
follows: Ten males: total length, 263 (230-280) ; tail vertebrae, 66 (60-74) ; hind 
foot, 44 (41-45.5) ; ear from crown, 9 (7-11) ; greatest length of skull, 44.5 
(42.2-46.3) ; zygomatic breadth, 28.0 (26.4-29.5) ; interorbital width, 10.5 (9.7-11.0). 
Ten females: total length, 260 (240-288) ; tail vertebrae, 66 (55-74) ; hind foot, 43 
(40-46) ; ear from crown, 10 (S-13) ; greatest length of skull, 44.0 (41.3-46.5) ; 
zygomatic breadth, 28.2 (26.7-28.9) ; interorbital width, 10.4 (9.7-11.0). 

Relatively old individuals show greatest size, especially of skull, which also has 
acquired more conspicuous ridges and sharper angles. Males average a trifle larger 
than females. 

Weights. — Average and extreme weights, in grams, of twenty mature specimens 
from the Yosemite section of the high Sierra Nevada are as follows : Ten males, 222 
(125.5-285.0) ; ten females, 240 (172-305). Average, in ounces, both sexes, about 8. 

The example showing the least weight was fully adult, but was very lean. Like 
other ground squirrels this species varies greatly in weight according to the amount 
of fat present. Specimens taken in August and September are, as a rule, fattest. 

Type locality. — Donner, Placer County, California (Merriam, 1888, pp. 317-320). 

Distribution area. — Higher parts of the central Sierra Nevada (chiefly Hud- 
sonian life-zone), from vicinity of Independence Lake, Nevada County, south to 
southeastern border of Yosemite National Park in vicinity of Mount Lyell (see fig. 
18). Altitudinal range, from 11,800 feet (as on Mt. Conness) down on western 
flank of Sierras to as low as 8,100 feet (Porcupine Flat, Yosemite Park) ; on easte n 
flank to as low as 6,500 feet, at western border of Mono Lake (Mus. Vert. Zool.). 

Specimens examined. — A total of 48 from the following localities in California: 
Nevada County : Independence Lake, 13. Placer County : "Johnson's Pass, High 
Sierras" [=^ Summit], 1. El Dorado County: Mt. Tallac, 1. Alpine County: Hope 
Valley, 4. Mono County : Mono Lake P. O., 1 ; Farrlngton's, Mono Lake, 3 ; Mono 
Pass, 1 ; Tioga Pass, 1 ; Walker Lake, 1. Tuolumne County : Tuolumne Meadows, 8 ; 
middle Lyell Canyon, 1 ; head Lyell Canyon, 5. Mariposa County : Mt. Hoffman, 
10,700 ft., 1 ; Tioga Road, southeast Mt. Hoffman, 3 ; near Vogelsang Lake, 2 ; two 
miles east Porcupine Flat, 1 ; one mile east Lake Merced, 1. 

This species of ground squirrel was named after Lyman Belding, an 
early resident of Stockton and a naturalist of considerable attainment. 
Belding found it in the summer of 1885 in the vicinity of Summit, 
Placer County, and sent a specimen to Dr. C. Hart Merriam, who later 
(1888) described the species, calling it Spermophilus beldingi. 

The most notable thing about the Belding Ground Squirrel is the 
great altitude of most of the area it inhabits. It is very closel}' restricted 
to the alpine meadows of the high central Sierra Nevada. The warmer 
levels below seem to be just as inimical to its welfare as the cold upper 
zones certainly are to the other ground squirrels which inhabit the 
middle slopes or foothills. Reference to our diagram (fig. 23) will 
show some interesting facts in this regard. We would infer that the 
Belding Ground Squirrel is the hardiest of all our species as regards 
ability to endure long and cold winters, though here the habit of hiber- 
nation must come importantly into play as tiding it over the extremes. 

This squirrel occurs in fair abundance on the preferred portions of 
its general range, namely, the grassy meadows in the neighborhood of 
timber line. Individuals rarely occur down as low as the belt of red 
firs and aspens (Canadian zone) on the west slope of the Sierras, though 
on the east slope a few do occur down through the Jeffrey pine belt. 
It is quite strictly an inhabitant of open levels; it is rarely or never 
seen in the woods or on steep or rocky slopes. Occasionally an indi- 
vidual ascends to the top of some glacier-borne boulder out in a meadow 
for a look around, but we have yet to observe any greater exploit in 
climbing. 



THE GROUND SQUIRRELS OF CALIFORNIA. 



661 




(a) Oregon Ground Squirrel in 
meadow near Klamath Falls, Oregon. 
Photographed by H. C. Bryant, May 30, 
1914. Note uniform coloration with 
no indication of a reddish brown patch 
on back. 



(b) Female Belding Ground Squirrel 
at entrance to burrow ; Tuolumne 
Meadows, Yosemite National Park. 
Photographed by T. I. Storer, July 27, 
1915. Note patch on back rendered 
photographically nearly black, but 
which was reddish brown. Compare 
with a. 




(c) Same squirrel as shown in b 
standing upright in characteristic 
"picket-pin" attitude. 



(d) Sierra Golden-mantled Ground 
Squirrel or "bummer," feeding on 
scraps from the camp table. Note the 
distended cheek. Bullfrog Lake, 10,600 
feet, Fresno County. Photographed by 
J. Dixon, September 1, 1916. 



FIG. 20. 



662 THE MONTHLY BULLETIN. 

Probably because of the open nature of their forage ground, these 
squirrels seem exceptionally timid. The shrill cries of alarm greeting 
the invader of a meadow upon his approach are quickly followed by 
total disappearance of the animals, at least for the time being. Each 
individual seems not to wander usually more than a few yards from 
the mouth of its burrow, so that but a short run intervenes at any 
moment between it and safety. The tail is held down when running, 
not elevated nor waved. The gait is rather slow and clumsy, impressing 
one observer as resembling that of a short-legged dog. ^' "Where the 
grass is short there is little up-and-down movement of the body shown 
in running; but in high grass, instead of parting the stalks and pressing 
them aside as it progresses, the animal advances by a series of jumps 
each of which carries it up clear of the grass so that it can glimpse 
about for a possible enemy" (T- I. Storer, MS). 

When within but a few feet of the mouth of its burrow and first 
taking alarm, a squirrel will rise quickly on its haunches and assume 
the rigid, upright, "picket-pin" posture (see fig. 20c). This usually 
brings the animal's head well above the grass tops, so that it can get a 
good view all about. Also it can then be seen a long way, looking in 
the distance like a tent-stake or picket-pin out on the meadow. During 
this pose the fore limbs are pressed closely against the body. Some- 
times the animal rises still higher, supporting its whole body on its hind 
feet and using its stubby tail as a prop (C. L. Camp, MS). The fact 
that the nose is continually twitched up and down, as if the animal 
were drawing in air, suggests that the sense of smell may be keen and 
that it may be used to determine the nature of a supposed enemy. If 
the observer continues his approach the squirrel suddenly deserts its 
"picket-pin" pose and dashes for its burrow, where it may hesitate a 
moment on all fours for one final look before diving out of sight. 

The voice of this squirrel closely resembles that of the Oregon Ground 
Squirrel. The usual call of warning consists of a series of from five to 
eight short shrill whistles uttered in quick succession and weakening 
toward the last. Females warn their young when foraging abroad with 
a lower-pitched, double note, or bark, e-cherV . A single note, sirt, is 
also frequently heard. 

The burrows of the Belding Ground Squirrel are generally located 
in the meadows which form their forage grounds. Sometimes, near 
timber line, one finds them in the scant gravelly soil between granite 
boulders, but always in or near patches of the kind of bunch grass 
occurring at such altitudes. The mounds are rarely conspicuous, and 
the holes open up to the surface steeply. Often there is no surplus 
earth at all around the mouths of the burrows, but this condition might 
be accounted for by the effects of M^ashing from heavy rain or melting 
snow. Several measurements of burrows gave an average diameter of 
two inches. The extent of the underground burrow system has only 
been tested out in one instance (see fig. 21). In this case the burrow 
was located in a wet meadow, snowbanks melting all about at the time 
(June 28), and it proved to be shallow, reaching an extreme depth of 
only about thirteen inches. But blind branches directed downward 
indicated the probability of greater depth later in the season when the 
water table had lowered and the soil dried out. The total length of 
this burrow system, including all its branches, was close to 54 feet. 



THE GROUND SQUIRRELS OP CALIFORNIA. 663 

^ 4 6 ^ '0 'X- '-^ _££ 




rZ 



Fig. 21. Plot of a used burrow belonging to a 
female Belding Ground Squirrel, as excavated by 
J. Grinnell and T. I. Storer in a meadow near the 
Tioga Road, on Snow Flat, 8,700 feet altitude, 
Yosemite National Park, June 2 8, 1915. 

Main opening of burrow at a (down this the 
squirrel went when shot, and was subsequently 
found at c) ; two other openings at a' and a" ; at h 
and 6' blind branches directed downward (the squir- 
rel may have essayed to dig deeper at these points 
but was discouraged by water) ; food materials, 
including lily tubers, in chamber at f ; in the enlarge- 
ment at the point marked nest was an accumulation 
of dry grass, the remains of an old nest or the 
beginning of a new one (the young would not have 
been born for about two weeks) ; boulder at g 
bulged out over the portion of the burrow adjacent 
to it, affording protection to the supposed nest- 
chamber. 

Diameter of burrow, 45 to 65 millimeters; average 
Df several measurements, 52. Average depth beneath 
surface of ground, about 135 mm. Greatest depth, 
at h and h', 330 and 270, respectively. Total length 
of system, about 54 feet. 



The burrow system above described belonged to just one squirrel, an 
adult female, which was found to contain five embryos, the only exact 
evidence we have as to the number of young to a litter. This was at 
8,700 feet altitude, on Snow Flat, Yosemite Park, on June 28. Half- 
grown young were common on Tuolumne Meadows, 8,600 feet, July 16. 
Young two-thirds grown have been taken at Independence Lake, Nevada 
County, 7,000 feet altitude, as early as July 13. Three third-grown 
young were seen, and one of them photographed (fig. 22) , at 6,800 feet 
altitude near Williams Butte, Mono County, June 28. There is thus 
probably some variation in time of appearance of the young, with alti- 
tude, the animals at the highest levels being born latest in the season. 
The young are out quite generally by the 15th of July. Only one litter 



71 



664 



THE MONTHLY BULLETIN. 



is born each year. On July 31, on Tuolumne Meadows, Yosemite Park, 
young Picket-pins were out in parties of six mostly, and sat about the 
mouths of their burrows or foraged in the very near vicinity. When 
frightened all members of each group darted for their refuge at the 
same time, crowding into the hole with some difficulty. 

Belding Ground Squirrels become very fat in late summer and hiber- 
nate regularly ; but exact dates of beginning hibernation in the autumn 
and emerging in the spring are wanting. We do know that they are 
not averse to running about over the surface of the snow at high alti- 
tudes in June, and so probably come out much earlier, and that in one 
year, 1915, they were still out as late as October 7 in the vicinity of 
Ten Lakes, Yosemite Park, although a light snowfall had already 
occurred. They were numerous on the extensive meadows in Tioga 




Fig. 22. Third-grown young Belding Ground Squirrel; photographed by J. Dixon, 
June 28, 1916, near Williams Butte, Mono County. 

Pass on September 28. It is evident that, in spite of its more elevated 
habitat, the Belding Ground Squirrel goes into its winter sleep a full 
two months later than the Oregon Ground Squirrel. 

Like the Oregon Ground Squirrel, the Belding feeds largely on grass 
stems and blades. An individual has been seen gathering seeds from 
grass heads, pulling the latter down to its mouth with its fore feet; 
but it is certainly not the seed-eater that the California and Golden- 
mantled ground squirrels are. Neither is there evidence that the Belding 
stores up much food. As with the Oregon species, its cheek-pouches 
are small (see fig. 13b). At Soda Springs, on Tuolumne Meadows, the 
Belding Squirrels have been seen foraging like rats about the mule 
corral. 

72 



THE GROUND SQUIRRELS OF CALIFORNIA. 665 

The enemies of this species of squirrel probably include most of the 
carnivores of the high mountains. A Mountain Weasel (Mustela an- 
zonensis) has been seen to kill one by biting it through the back of the 
neck (C. L. Camp, MS). 

The Belding Ground Squirrel bears no decided economic importance, 
save as might be involved in the grass it eats. Its habitat falls only 
within the summer range of sheep and cattle, and its numbers are 
nowhere so great as to be likely to reduce the crop of pasture grass 
to any material extent. 



STEPHENS SOFT-HAIRED GROUND SQUIRREL. 
Citellus mollis Stephens! (Merriam). 



other names. — Stephens Spermophile ; Picket-pin, part ; Stephens Ground Squir- 
rel ; Spermophilus mollis stephensi. 

Field characters. — Small size combined with very short and slender tail and gray 
coloration (no stripes or special markings) ; ear small; length of body alone about 6^ 
inches, with tail about 2 inches more. 

Description. — Nearly full-grown young in summer pelage (June) : General tone 
of coloration on upper surface of body, buffy gray ; top of head from nose to hind 
neck, pale cinnamon-buff, deepest on nose, and changing into color of back on 
shoulder ; cheek to shoulder, olive-buff ; eyelids white ; whiskers black ; back light 
drab with a faint effect of fine dappling ; the hairs on the back lead-colored at extreme 
bases, then gray, then bister, and tipped with buffy white. Upper surfaces of feet 
dull white ; palms naked ; soles of hind feet clothed with dull whitish hairs to about 
halfway forward from heel ; claws blackish, with horn-colored tips. Tail flat-haired, 
but narrowly so, and tapering from base to tip ; upper surface bufify drab ; beneath 
dull white at base, becoming dusky pinkish buff toward end. Lower surface of body 
silvery white, faintly buff tinged, particularly as forming a band along each side, and 
with much of the leaden-hued bases of the hairs showing through. 

We have at hand but two specimens of this ground squirrel, and these are both 
immature. 

Color variations. — A considerable series of specimens of Citellus mollis (sub- 
species?) at hand from northern Nevada make it seem likely that stephensi varies 
in color but little from the coloration as here described ; probably old adults are 
grayer, with little or none of the cinnamon-buff about the head. The summer pelage 
at all ages is notably soft and silky as compared with that of most other species of 
ground squirrels at the same season. There is possibly a distinct winter pelage, with 
regular molts in spring and fall ; but we have no specimens to indicate this. 

One of our two specimens has the tail much flatter, and broader ended, than 
the other ; but this we think is due to the way the tail was wired when the skin 
was prepared. The usual thing is for the tail to taper from base to tip, thus quite 
unlike the condition found in the Mohave Ground Squirrel. 

Measurements. — Nine specimens from the head of Owens Valley, in California, 
average, in millimeters as follows : total length, 212 ; tail vertebrae, 50 ; hind foot, 
32.4 (Merriam, 1898, p. 70). 

The two immature specimens in the Museum of Vertebrate Zoology, from near 
Mono Lake, measure as follows, the first figures given being for the male, the second 
for the female : total length, 195, 185 ; tail vertebrae, 45, 45 ; hind foot, 32, 82 ; ear 
from crown, 4, 4; greatest length of skull, . . ., 35.6; zygomatic breadth, 21.8, 22.0; 
interorbital width, 7.4, .... 

Weights. — Our two specimens weigh, in grams, as follows: male, 83.6; female, 78.0 
(in ounces, about 3 and 2f, respectively). 

Type locality. — Queen Station, near head of Owens Valley, Nevada [in Esmeralda 
County, just across California boundary] (Merriam, 1898, p. 69). 

73 



66b THE MONTHLY BULLETIN. 

Distribution.-— Within the state of California, in only a very limited area com- 
prising the sagebrush valleys of eastern Mono County, namely from southeastern 
edge of Mono Lake to head of Owens Valley in vicinity of Benton Station (see fig. 18). 
Life-zone, Upper Sonoran chiefly, barely entering Transition locally (see fig. 23). 
Southernmost known locality of occurrence, Taylor Ranch, in Owens Valley, two miles 
south of Benton Station. Altitudinal range, 5,300 to 7,300 feet. 

Specimens examined. — A total of 2, both from Mono County : Mono Mills, 1 ; Dry 
Creek, 1. 

The Soft-haired Ground Squirrels belong to the Great Basin region 
of the western United States and get into our California list only on 
the basis of the occurrence of one of the subspecies, the Stephens, in a 
few places along the eastern border of the state. This is a distinctly 
different type of ground squirrel from any of our others, notably in the 
soft, silky ''feel" of the hair. In addition, the small size, short slender 
tail, and uniform light grayish coloration make a combination of- 
characters which is unique among our species. 

Unfortunately, our own personal experience with this species has 
been very limited. In September of 1917 the two of us made especial 
search for it at the extreme head of Owens Valley. But we were too 
late in the season; locally well known in the vicinity of Benton, we 
were assured by the ranchers that the animals had all "holed up" by 
about the end of July. On the Pellisier Ranch, five miles north of 
Benton Station, ''Picket-pins" were declared to have been present "by 
the million" from April until July, but it was averred that by the last 
of August they had all disappeared. Numerous round holes in the 
ground among the sage bushes were pointed out to us as belonging to 
these squirrels. There was abundant evidence that coyotes and badgers 
regularly dig them out. Also we were told that at the season the 
squirrels are above ground the Indians capture many for food. 

On the Taylor ranch this squirrel was reported to be plentiful, but 
to vary much in numbers from year to year. In the spring of 1916 it 
was abundant; in 1917 scarcely any were seen. 

In the sand-dune area along the east side of Mono Lake, the junior 
author saw several Soft-haired Ground Squirrels on June 10, 1916. 
The sand was fairly covered with their tracks. Those individuals seen 
on June 11 near Dry Creek in the same neighborhood were notably 
tame. They gave the impression of being flat-bodied, and slid along 
the ground like lizards, stopping to scrutinize the intruder from the 
shelter of the first bush reached. One was captured under a bush by 
being pinned down with the gun. 

Mr. Frank Stephens of San Diego, for whom this subspecies was 
named, states (1906, p. 71) that he found the animals "rather common 
in the valleys of eastern Mono County." They were feeding on the 
sagebrush and were exceedingly fat. The date of capture of the type 
was July 12, 1891 (Merriam, 1898, p. 69). 



74 



¥^»' 











# 



THE GROUND SQUIRRELS OP CALIFORNIA. 667 

MOHAVE GROUND SQUIRREL. 
Citellus mohavensis (Merriam). 

PLATE IV. 



Other names. — Mohave Desert Spermophile ; Mohave Desert Ground Squirrel, part ; 
Spermophilus mohavensis ; Citellus tereticaudus mohavensis, part. 

Field characters. — A small-sized, hrown-colored ground squirrel, without stripes 
or special markings whatsoever on the body, but with short broadly haired tail, 
white underneath ; ear a mere rim ; length of body alone, about 62 inches, with tail 
about 2^ inches more. 

Description. — Adult in full winter pelage: General tone of whole upper surface 
from nose to base of tail cinnamon drab ; hairs on back when examined closely are 
seen to be lead-color at base, then ashy white, then army brown, and tipped with 
white ; mixed with these hairs are a few of solid black color, and on the rump some 
which are black with a white interval near end. Eyelids white, but cheeks like 
back ; rim of ear and upper sides of feet tinged with light pinkish cinnamon ; palms 
of fore feet naked ; soles of hind feet clothed with long buffy hairs ; claws black with 
horn-colored tips. Under surface of body srlvery white, but slaty bases of hairs show 
through making the general effect light gray. Under surface of the flattish stubby 
tail pure white ; upper side like back at base, becoming mixed black and white toward 
end ; extreme end with white fringe. Adult in summer pelage : Coat very much 
coarser and shorter than in winter ; general color tone browner, close to cinnamon, 
but a grizzling effect is produced by white hair-tippings everywhere on upper surface. 
Sides of face paler than in winter, and lower surface of body pure white, owing to 
lack of lead-color at bases of individual hairs. 

Color variations. — Specimens of dates May 3 and 12 are in process of molt from 
winter to summer pelage. Patches of worn and yellowed winter hairs remain on the 
fore back and rump. The tail is seemingly not included in the spring molt, and the 
old tail hairs become crinkled and broken at the ends ; the white of the under side 
is dingy, and a dark subterminal band around the end of the tail shows through. 

Measurements. — Average and extreme measurements, in millimeters, of seven adult 
specimens (5 males, 2 females), from the northern part of the Mohave Desert are 
as follows: Total length, 224 (212-230) ; tail vertebrae, 62 (42-72) ; hind foot, 36 
(34-37) ; greatest length of skull, 3S.6 (38.1-39.0) ; zygomatic breadth, 24.3 
(23.6-25.3) ; interorbital width, 8.7 (8.2-9.2). 

The two sexes appear to be alike in measurements as well as in coloration. 

Weights. — An adult male, not particularly fat, was found to weigh J04 grams 
(about 3| ounces). 

Type locality. — Mohave River, California (Merriam, 1889, p. 15). More exactly, 
near Rabbit Springs, about 15 miles east of Mohave River at Hesperia, in San 
Bernardino County (Stephens, in conversation, January 1, 1916). 

Distribution area. — Not continuous ; western parts of the Mohave Desert, from 
Haiwee, Inyo County, south to Rabbit Springs, San Bernardino County (see 
fig. 18). Life-zone, Lower Sonoran, though only in its upper portion apparently. 
Altitudinal range, 2,500 to near^ 4,000 feet. 

Specimens examined. — A total of S, from the following localities in California: 
Inyo County : Haiwee Meadows, 3,750 feet alt., about teu miles south of Owens Lake, 
2 (in coll. U. S. Biol. Surv.) ; Little Lake, 3,100 feet, 2 (Mus. Vert. Zool.). San 
Bernardino County: Salt Wells Valley (eastern edge near Inyo County line), 2,500 
feet, 3 (U. S. Biol. Surv.) ; Rabbit Springs, 2,900 feet, east of Mohave River, 1 (in 
coll. F. Stephens). 

The Mohave Ground Squirrel, although first discovered in 1886 by 
Mr. Frank Stephens of San Diego, has remained about the least known 
of all our rodents. Only four rather scattered localities of occurrence 
are definitely known, as listed above under "Specimens examined." 
The dates represented are March 22 and 24, May 3 and 12 and June 5. 



668 THE MONTHLY BULLETIN. 

The two specimens in the Museum of Vertebrate Zoology were trapped 
on the first two specified dates, in 1918, on the hillsides immediately 
west of Little Lake. They were daytime-taken in oat-baited rat-traps 
set beneath creasote bushes on gravelly ground. In spite of diligent 
search by the collectors everywhere in the neighborhood, not one of this 
species was seen alive. No information is available to us in regard to 
either behavior or food. 

This ground squirrel is altogether distinct from Citellus tereticaudus. 
There is no indication of intergradation with that species, as stated by 
Elliot (1904, p. 291). In fact, the animals reported by that author 
from Daggett were all probably in reality tereticaudus, which species is 
known to us to be present at Daggett. The tail of mohavensis is always 
much shorter and more broadly haired than in tereticaudus, the claws 
are stouter, the cheeks are brownish instead of white, the under side of 
the tail is white, instead of buffy with brown mottlings toward the end, 
the quantity of winter pelage is greater, and the general tone of colora- 
tion is always decidedly dark. 

The fact that the under side of the tail is white, as in the Antelope 
Ground Squirrel, leads us to suspect some such special habit of display- 
ing this member as is possessed by the latter animal. But this is mere 
speculation. The relationships of mohavensis as indicated by structural 
features are thought to lie rather with Citellus than with Ammosper- 
mophilus. 



YUMA ROUND-TAILED GROUND SQUIRREL. 
Citellus tereticaudus tereticaudus (Baird). 



PLATE IV. 



other names. — Round-tailed Spermophile ; Yuma Ground Squirrel ; Mohave 
Desert Ground Squirrel, part; Spermophilus tereticaudus ; Xerospermophilus tereti- 
caudus; Citellus tereticaudus mohavensis, part. 

Field characters. — A small ground squirrel, of slender build, and of pale brown 
color (no stripes or other markings) ; tail long and slender, not broadly haired; ears 
very small, mere rims ; length of body without tail about 6 inches, with tail about 
3f inches more. 

Description. — Adult in winter pelage : Whole upper surface from nose to and 
including tail, light pinkish cinnamon in general tone ; individual hairs lead-colored 
at extreme bases, then dull white, then pinkish cinnamon, and with tipping of white. 
Eyelids and whole lower surface to root of tail, white; side of head and neck 
including ear dull white ; whiskers black ; hairs of belly lead-colored at extreme bases. 
Upper surfaces of feet dull buffy white ; claws dark brown basally, becoming horn- 
color at tips ; soles of feet haired save for under sides of toes. Tail cylindrical in 
shape, a little more heavily haired toward end than at base ; under side dull buff, with 
black mottlings in fine pattern toward end ; above like back on basal half, becoming 
black and buff mottled toward end ; hairs at tip of tail brown at their bases, then buff, 
then broadly black, and with white ends. 

Adult in summer pelage : Coat short and harsh as compared with winter coat ; 
color above brighter pinkish cinnamon. Otherwise as in winter, but the tail, which 
apparently does not molt, pale brown and still slenderer, due to the fading out of the 
dark colors and to the wear and consequent shortening of the hairs. 

Color variations. — Young partly grown are colored like summer adults, but the 
pelage is not quite so harsh and on the under surface is so sparse as to allow 
the bare skin to show through in places. There are two molts in the adults each year 

76 



THE GROUND SQUIRRELS OP CALIFORNIA. 669 

and two distinct pelages separated by these. The spring molt occurs during April 
(March 2S to May 1 according to specimens at hand), and the fall molt probably 
during October though there are no specimens available to show its extent. The 
remnants of the winter pelage during the spring molt become faded in some specimens 
to a dull yellowish tone. This molt advances in a general way from the front back- 
ward, but specimens often show a patchy or mixed coat on the back and rump. 

Measurements. — Average and extreme measurements, in millimeters, of seventeen 
adult specimens from the Colorado and Imperial valleys are as follows : seven males : 
total length, 247 (225-261) ; tail vertebrae, 95 (S5-107) ; hind foot, 36 (34-37) ; 
greatest length of skull, 37.1 (35.2-38.2) ; zygomatic breadth, 23.5 (22.5-24.4) ; 
interorbital width, 8.9 (8.3-9.5). Ten females: total length, 241 (216-258); tail 
vertebrae, 91 (75-102) ; hind foot, 36 (33-38) ; greatest length of skull, 36.0 
(34.3-3S.2) ; zygomatic breadth, 22.2 (21.3-23.4) ; interorbital width, 8.6 (8.0-9.5). 

Males are seen to be slightly larger than females. The ears in this species are 
small, the rims rising not more than 3 millimeters (i inch) above their inner base. 
In but few specimens did the collector attempt to secure the measurement of the ear. 

Weights. — Stephens (MS) found two females and a male to weigh together 12 
ounces, an average of 4 ounces each. "All were thin." 

Type locality. — Fort Yuma [Imperial County], California (Baird, 1857, pp. 
315-316). 

Distribution area. — Low-lying sandy areas on the Colorado and Mohave deserts. 
Life-zone, Lower Sonoran (see fig. 23). More specifically: the Imperial Valley west 
as far as La Puerta (Mus. Vert. Zool.) in extreme eastern San Diego County, north 
to the southern end of Salton Sea, and east to old Fort Yuma ; thence north along 
the Colorado River nearly or quite to the Nevada line ; and from the vicinity of 
Needles and Blythe, iu the Colorado Valley, northwestward across the central part of 
the Mohave Desert to at least as far as Kramer (Grinnell, MS), in west-central 
San Bernardino County. Altitudes of occurrence, from 200 feet below sea-level to 
2,300 feet above. The range of this species is not continuous over the area just 
indicated (see fig. IS), but consists of many colonies more or less distantly isolated 
from one another. 

Specimens examined. — A total of 28 from the following localities in California: 
San Bernardino County, one-half mile north of Barstow, 1 ; Daggett, 1 ; Blythe 
Junction, 4 ; Needles, 3. Imperial County : south end of Salton Lake, 6 ; six miles 
south of Holtville, 2 ; Coyote Well, 4 ; Pilot Knob, 4 ; Colorado River opposite Cibola, 
2. San Diego County : La Puerta, 1. 

The Yuma Round-tailed Ground Squirrel was first made known to 
science in 1857 from specimens taken by an army officer stationed at 
old Fort Yuma, which was situated on the California side of the Colo- 
rado River opposite the present town of Yuma. It inhabits the hottest 
of our southeastern desert valleys. Its metropolis lies in the Imperial 
Valley and thence north along the valley of the Colorado ; a few colonies 
occur also on suitable parts of the Mohave Desert. Over this general 
region tlie species is by no means continuously distributed. It seems to 
be very particular in its requirements, only level ground of a sandy 
nature being as a rule inhabited at all. Places are preferred where 
wind-drifted sand has been accumulated into mounds about the bases 
of mesquite, creasote bushes, or salt bushes. Here the burrows are to 
be seen opening up among the stems of the partly buried shrubs; and 
the animals, if not actually seen themselves, are shown by their tracks 
in the sand surface to be in the habit of foraging out across the bare 
intervals for the seeds which are to be found sifted among the sand 
particles. 

The squirrels themselves are usually shy and by reason of their 
obscure coloration and especially the shimmering glare on the desert 
surface are not readily observed unless particularly sought for. Neither 
are their total numbers very great even where conditions are fairly 



670 



THE MONTHLY BULLETIN. 



favorable. While our observations show them to be strictly diurnal in 
habits, we have noted an apparent aversion to direct sunshine. Perhaps 
this is because the sunshine on the desert is in summer so intense as to 
be quickly fatal to any small animal exposed to it for long. We know 
for a fact of squirrels caught in traps by one foot or merely a toe, on 
open ground, which have quickly succumbed — "sun-cooked" is the 



Lower 
6onoran 



Upper 
donoran 



Transition 



Canadian Hudeon, 



Arctic 



Qikllu5 -beecheui beecheiji 



Cifellus beech eyi fich&ri 



Cife//u5 beechQLf'i nedoticuQ 



Cilellu.6 douglao/i 



Cifellus van'egatug grammuras 



Cifellus ore gonu6 



Ci/ellu5 beld/'ngi 



Cifellui> mollid slephensi 



Cifellus mohaVensis 



Cilcllus ferelicaudus fereficaudus 



Cifellus lerelicaudus erewonomua 



Cifellus iereficaudus chlorud 



Callospermophilus chrysodeirua chrgsodeirus 



Callospermophilus chrysodeirus perpalfidua 



Callospermophilud chrysodeirus bernardinus 



Qmmospermophilus feucurus feucurue 



Qmmospermophilue nelson! nelson! 



Qmmo6permopfiilu6 nelson i am pi u 5 



Fig. 23. Diagram showing the ranges of the ground squirrels of California accord- 
ing to life-zones. (For life-zone map of California, see Grinnell, 1913, pi. 15.) 

term we use for such victims. At any rate, the squirrels are seen 
crossing open spaces but momentarily, and thenceforth they remain in 
the shade of bushes until they take final alarm and descend into their 
burrows. 

The long, slender, ratlike tail is exclusively characteristic of this 
species of ground squirrel. The body, too, is rather slender, though 
after a full meal of green stuff individuals have been seen which showed 
a rather pot-bellied outline. The mere rims of ears give the animal a 
round-headed look. The movements are rather more agile than in most 
of its relatives. It not infrequently climbs up into bushes to a height 
of four or five feet, but here it becomes clumsy. 

The voice of the Round-tailed Ground Squirrel is unmistakable when 
once learned. As far as known to us, but one kind of note is uttered, a 
single high-pitched squeak or shrill whistle, seep, uttered only at rather 
long intervals, never in a series as with some others of the ground 
squirrels. The quality of this call is such that the direction from which 

78 



THE GROUND SQUIRRELS OP CALIFORNIA. 671 

it emanates is difficult to fix; also the distance is hard to determine. It 
seems to be given as a Avarning by an individual, either located Avithiu 
the mouth of its burrow (Stephens, 1906, p. 70) or Avhen standing 
motionless under a bush. C. L. Camp (MS) records that he has seen 
an individual, when its curiosity was aroused, stand high up on its hind 
legs and utter its "sharp squeak" with the mouth wide open, at the 
same time "giving the thorax a violent contraction." 

Facts in regard to the breeding of this squirrel are shown in the 
following data. On March 15 (1914) near Barstow a male Round- 
tailed Ground Squirrel was seen abroad which proved astonishingly 
indifferent. "It came up to where we were digging out a kangaroo rat 
colony, smelling into various burrows, evidently intently hunting for a 
female. The testes of this animal were enormous, dragging on the 
ground behind it as it waddled along" (Grinnell, MS). Two females 
captured in the valley of the Colorado River opposite Cibola, April 3 
and 4 (1910) , were found to contain six and four embryos, respectively ; 
young about half grown were taken at Needles July 15 and 19 (1909) 
(Grinnell, 1914, p. 224). Stephens (1906, p. 70) says that the breeding 
season falls in March and April and that the number of young in a litter 
is four to seven. In spite of the long hot period each year in the habitat 
of this species, there is no evidence to show that more than one litter 
is reared annually. 

There is a period of inactivity during midwinter, when these animals 
are not seen abroad. Whether or not there is regular hibernation, as 
with the species of colder regions, we do not definitely know; but this, 
seems to be the case. 

"The food is seeds the greater part of the year; these are stored to 
some extent. In the spring, during the few weeks when green vegetation 
is obtainable, leaves and buds are eaten voraciously" (Stephens, 1906, 
p. 70). In our experience, stems of the squRw-teai (Ephedra) and 
leaves of the mesquite form an important element of the diet wherever 
and whenever obtainable. 

In June, 1918, W. C. Jacobsen (MS) found several colonies of Yuma 
Round-tailed Ground Squirrels in the Imperial Valley within five or 
six miles south of Holtville. The interesting thing was that here the 
animals were invading the cultivated fields and were finding alfalfa 
suited to their tastes. Individuals were seen to eat the leaves of the 
alfalfa with avidity, but left the stems uneaten. Many dry stems were 
found lying about near the mouths of their burrows. At another 
point, near Bond Corners, oat hulls were seen around burrows.' 

There is a possibility, therefore, that this strictly desert rodent might 
come to have an economic bearing on the reclaimed sections of the 
desert. Whether or not it will become a serious pest remains to be seen. 
One note of interest in this connection is furnished by Stephens (MS), 
who says that at Silsbee, while occasionally getting into the fields, the 
Round-tails were easily drowned out. As far as known to us, this 
species never drinks water even when within reach of it; In most parts 
of its range and at most seasons of the year water is secured only 
through chemical elaboration from its dry or nearly dry food materials. 
It is currently reported by the farmers in Imperial Valley that the 
native desert animal life quickly disappears when the land is brought 
under cultivation and especially irrigation. 



672 THE MONTHLY BULLETIN. 

DEATH VALLEY ROUND-TAILED GROUND SQUIRREL. 
Citellus tereticaudus eremonomns Elliot. 



Other names. — Death Valley Spermophile ; Citellus eremonomus. 

Field characters. — Exactly as for the Yuma Round-tailed Ground Squirrel. 

Description. — As for the Yuma and Palm Springs Round-tailed Ground Squirrels, 
but coloration decidedly darker than in either, near wood brown. This feature is 
characteristic in all of the eight skins of eremonomus at hand. 

Color variations. — The time of the spring molt is indicated by a specimen of date 
April 10, in which new summer pelage shows on the head and rump ; an example of 
May 3 is in absolutely new summer pelage except, of course, for the tail. One speci- 
men has a bobbed tail, with an abnormal tuft of hairs at the end, showing con- 
spicuously a band of black and then a terminal band of white. Most of the skins 
show a curious spotting of the rump which is clearly not due to color markings on 
the hairs, but to places where hairs are absent, so that the dark-colored skin and dark 
bases of adjacent hairs show through. These may indicate scars from insect bites. 

Measurements. — Average and extreme measurements, in millimeters, of eight adult 
female specimens from Death Valley are as follows: total length, 249 (240-255) ; 
tail vertebrae, 91 (87-93) ; hind foot, 35 (34-36) ; ear from crown, 2.1 (2.0-3.0) ; 
greatest length of skull, 36.0 (34.8-36.6) ; zygomatic breadth, 22.5 (22.0-23.4) ; 
interorbital width, 8.7 (8.3-8.8). No males are available. 

Weights. — Average and extreme weights, in grams, of eight adult females from 
Death Valley are as follows: 144.3 (121-158). The average, in ounces, is 5.1. 

Type locality. — Furnace Creek [Ranch], Death Valley, Inyo County, California 
(Elliot, 1903, p. 243). 

Distribution area. — Floor of Death Valley, in Inyo County. Life-zone, Lower 
Sonoran. Only known locality of occurrence, vicinity of Furnace Creek Ranch 
(Greenland Ranch), — 240 to — 175 feet altitude. Apparently cut off from its nearest 
relative, tereticaudus proper, by the elevated rim of the Death Valley basin. 

Specimens examined. — A total of 8, all from the near vicinity of Furnace Creek 
Ranch, — 178 feet. Death Valley, Inyo County. 

As far as known, this race of Round-tailed Ground Squirrel is limited 
in its distribution to the bottom of the deep sink known as Death Valley, 
and even there to the belt of mesquites immediately around the margin 
of the alkali flats at the lowest level. The entire habitat of this Death 
Valley subspecies thus lies below sea level, a distinction probably not 
shared by any other rodent in America. 

Our experience with this squirrel was obtained during April and 
early May, 1917, in the immediate vicinity of old Furnace Creek Ranch, 
now known as Greenland Ranch. The animals at the time of our visit 
were not invading the cultivated land, though we were assured by the 
foreman that they had come into the alfalfa fields in previous seasons. 
Since this was the type locality of the subspecies, special efforts were 
made to obtain a series of specimens. The animals were not abundant, 
and proved practically impossible to trap. Shooting was resorted to, 
though with but little better results. The following notes were made 
on April 10 by the senior author while hunting them. 

During a two hours hunt at midday at least five individuals were 
heard on the mesquite-crowned sand dunes within a mile southwest of the 
ranch. The warmth had seemingly brought them out, for the previous 
two or three days had been relatively cool, and none had been seen. 
A temperature of over 100° in the shade seemed to be necessary to 



THE GROUND SQUIRRELS OF CALIFORNIA. 673 

bring the animals out into full activity. ' ' I caught sight of one standing 
upright at the mouth of its burrow, squeaking, and of two others run- 
ning over the sand beneath the trailing green mesquite branches. The 
lines of footprints in the sand centering at the mouths of their burrows 
are diagnostic. The animals are extremely shy, going below ground 
at the slightest alarm. By standing ten minutes or so 'at attention' 
about fifteen yards from the mouth of a burrow down which one van- 
ished, I finally saw the top of its head reappear to the level of its eyes. 
This position was maintained for many minutes, until the animal 
suddenly raised its whole head and neck into view, when I shot it. 

''Later, while I was lying prone on the sand under a mesquite, one 
came up to within eight feet of me and gave its shrill, wiry cry, or 
squeak. A mere movement on my part, and it vanished, quick as 
thought." It was found that a little "screeping" (lips to back of 
hand) would often bring one of the squirrels stealthily investigating 
through the brush, provided the observer kept perfectly motionless 
himself and was possessed of patience. The squirrel would sometimes 
squeak, apparently in answer, and thus be called into very close "aux" 
range. The burrows were as a rule located in the periphery of a large 
mesquite clump, where they were shaded by the radiating leafy branches 
which trailed down the sandy slopes. Not more than three burrows 
certainly of this rodent were to be found about any one clump. 

The mesquites during early April were just coming out into full new 
foliage. The stomachs of the squirrels shot were distended with masses 
of finely chewed mesquite leaves and nothing else. This, in fact, was 
absolutely the only kind of vegetation anywhere in sight for hundreds 
of yards. In one instance the total weight of the freshly killed animal 
was found to be 154.5 grams; of the full stomach alone, 28.7 grams, or 
19 per cent (near one-fifth) of the total weight. In other words, a 
Death Valley Round-tailed Ground Squirrel may eat close to one-fourth 
its own weight of green mesquite leaves. 

No young were seen by us up to the time of our departure, but they 
are probably born about the first of May. Tavo old females captured 
April 10 and 12 contained four and three embryos, respectively. 



PALM SPRINGS ROUND-TAILED GROUND SQUIRREL. 
Citellus tereticaudus chlorus Elliot. 



Other names. — Pale Spermophile ; Citellus cMorus. 

Field characters. — Exactly as for the Yuma Round-tailed Ground Squirrel. 

Description. — As for the Yuma Round-tailed Ground Squirrel, but tone of colora- 
tion more grayish, avellaneous rather than light pinkish cinnamon. This differencB 
holds through all pelages and gives the impression of an olive-colored animal, when 
close comparisons are made with series of the other related ground squirrels. 

Color variations. — Specimens showing the spring molt to be in process bear dates 
from March 29 to as late as June 3. As with the other races of tereticaudus the 
pelage on the tail is not replaced during the spring molt and it becomes greatly faded 
and worn. In extreme cases the tail with its shortened, singed-lookiug hairs is a 
dirty pale brown color throughout, and as slender as a wood-rat's tail. The summer 

. 6— 43C07 81 



674 THE MONTHLY BULLETIJN. 

coat is so short and thin that any scars there may be in the skin show through as 
dark spots. These appear irregularly on certain specimens, usually those which 
examination of the teeth shows to be the older individuals. 

Measurements. — Average and extreme measurements, in millimeters, of twenty 
adult specimens from Whitewater, Palm Springs and Mecca, in Riverside County, are 
as follows: Ten males: total length, 241 (220-251); tail vertebrae, 90 (79-97); 
hind foot, 36 (35-iO) ; greatest length of skull, 36.6 (35.2-.38.9) ; zygomatic breadth, 
23.0 (21.6-24.6) ; interorbital width, 8.9 (8.0-9.7). Ten females: total length, 240 
(229-264) ; tail vertebrse, 89 (80-102) ; hind foot, 35.7 (34-39) ; greatest length of 
skull, 36.1 (35.6-37.5) ; zygomatic breadth, 22.8 (22.0-23.4) ; interorbital width, 8.8 
(S.6>-9.4). 

Type locality.— Palm Springs, Riverside Coimty, California (Elliot, 1903, p. 242). 

Distribution area. — The northwestern arm of the Colorado Desert between Salton 
Sea and San Gorgonio Pass (see fig. 18). Life-zone, Lower Sonoran. More specifi- 
cally, the Coachella Valley, entirely within Riverside County, from Mecca northwest 
to Whitewater Station ; altitude from — 200 to 1,130 feet. 

Specimens examined. — A total of 41 from the following localities, all in Riverside 
County : Palm Springs, 6 ; Whitewater Station, 18 ; Mecca, 17. 

This race of Round-tailed Ground Squirrel was first made known from 
specimens collected in the vicinity of Palm Springs, out on the Colorado 
Desert near the northeast base of San Jacinto Peak. Subsequent 
exploration has shown it to be limited to the relatively small area of flat 
desert lying between Salton Sea and the upper part of San Gorgonio 
Pass, and shut in narrowly by the mountain walls on either side. 

The slight features by which this subspecies is distinguishable from 
the Yuma Round-tailed Ground Squirrel of the Imperial Valley south- 
east of Salton Sea may be inferred to have arisen as a result of the 
action of the body of water which formerly filled the Salton Sink to 
sea level in cutting off or isolating the animals in the northwestern arm 
of the Colorado Desert and thus giving them a chance to develop 
peculiarities all their own. The ancient predecessor of the present 
Salton Sea is known to geologists as Blake Sea, and this inland sea 
extended from the base of the Chocolate Range of mountains on the 
northeast to the very foot of the Santa Rosa Mountains on the south- 
west, thus constituting an impassable barrier to any animal closely 
restricted, as is the Round-tailed Ground Squirrel, to dry, level, sandy 
ground. However this may have been, the Palm Springs subspecies 
now ranges down the Coachella Valley from the northwest nearly to the 
upper end of the present Salton Sea, in the vicinity of Mecca. One 
can imagine the animal life of the desert floor now retreating, now 
advancing, with the fluctuations of the old Blake Sea since the time it 
was first cut off from the Gulf of California by the slowly growing delta 
of the Colorado. 

The general habits of the Palm Springs Round-tailed Ground Squirrel 
are probably closely similar to those of the Yuma and Death Valley 
animals. The first-named is fairly common locally, though it rarely 
forces itself on the attention; it has to be specially looked for. At 
Mecca in March and April (1908) one or two were caught nearly every 
day in oat-baited rat-traps set on sandy mounds beneath mesquites. 
Yet the animals themselves were rarely seen. On April 26 one was 
surprised up in a mesquite ; upon being shot it was found to have parts 
of a mesquite flower in its mouth. The senior author was told that at 
the experimental date farm near Mecca these squirrels had been seen 
eating the dates. 

82 



THE GROUND SQUIRRELS OF CALIFORNIA. 675 

At the railroad station of Whitewater this animal was found by 
museum collectors to be common, June 3 to 5 (1908), in a tract of sand 
dunes nearby. The shrill calls or whistles were heard frequently, and 
many of the squirrels were trapped. Some of these were young, one- 
third to one-half grown. The old males and part of the old females 
taken then were very fat ; all the rest lean. A female taken at Mecca, 
March 27, was found to contain five large embryos. The extent of the 
breeding season is thus indicated. Doubtless but one litter is raised 
each year. 

Search in the vicinity of Palm Springs in December and January of 
different years has failed to show the presence of these squirrels actively 
abroad; so that it is likely that they hibernate during midwinter. In 
1916, Swarth (MS) found them out on February 4 in a tract of sandy 
soil about a mile east of the village. They occurred in small scattered 
colonies, each ' ' colony ' ' marked by twelve to fifteen open holes on level 
ground among creasote bushes. ''Parts of the burrows were shallow, 
so that a person would sink through into them ankle deep." The 
animals when alarmed would scurry to their holes and disappear into 
them, but would presently poke up their heads and utter "faint little 
barks. ' ' 

No information has come to us that would indicate any decided 
economic bearing on the part of the Palm Springs Round-tailed Ground 
Squirrel. Because of its dry-land preferences it is likely that reclama- 
tion and irrigation of the land would drive it away rather than attract 
it. Thus the reaction would be just the opposite to that in the case of 
the Oregon Ground Squirrel and similar species. 



SIERRA GOLDEN-MANTLED GROUND SQUIRREL. 
Callospermophilus chrysodeirus chrysodeirus (Merriam). 

PLATE IN. 

other names. — Gilded Squirrel ; Gilded Ground Squirrel ; Copper-headed Ground 
Squirrel ; Copperhead ; Yellow-headed Chipmunk, part ; Golden Chipmunk ; Side- 
stripe Ground Squirrel ; Bummer ; Trinity Ground Squirrel ; Callospermophilus 
chrysodeirus trinitatis; Citellus chrysodeirus, part; 8permophilus chrysodeirus, part; 
Spermophilus lateralis; Callospermophilus lateralis chrysodeirus ; Citellus chrysodeirus 
trinitatis; Tamias chrysodeirus; Tamias lateralis, part. 

Field characters. — A medium-sized, ground-dwelling squirrel with conspicuous 
stripes along sides of body ; whole head more or less deeply yellow or coppery red ; 
build stout; length of body without tail about 7 J inches, with tail about 3A inches 
more. 

Description. — Adult in fresh late-summer pelage : Whole top of head and hind 
neck, orange-cinnamon ; cheek and side of neck to shoulder, ochraceous-tawny ; side 
of snout, area around eye, ear and spot behind ear, ochraceous-buff of varying inten- 
sity ; whiskers black. Two black stripes and an intervening buffy white stripe on 
each side of body ; the whitish stripe longest, extending from shoulder over side of 
rump nearly to base of tail ; the lower black stripe next in length, the upper shortest 
and it and its fellow of opposite side separated by a median band of grizzled light 
cinnamon-brown ; this band extends from between shoulders backwards to base of 
tail, and expands on rump to cover flanks ; side of body below lower black stripe, 
light buff, obscured by dusky hair-tippings. Upper sides of feet light buff: 



676 THE MONTI-ILY BULLETIN. 

claws blackish-brown, horn-color at tips ; soles of hind feet naked nearly to 
heel. Chin and throat and insides of forelegs and thighs buffy white ; belly with 
hairs extensively slaty brown at base, tipped with whitish ; in other words, whitish 
with much slaty brown showing through. Tail well-haired, flat in form, broadest in 
middle portion, tapering somewhat toward end ; in color, as viewed from above, 
chiefly black, with a margin of ochraceous-buff ; there is considerable mixture with 
cinnamon-brown toward base, however, and separation of the hairs discloses the 
deeper-lying hazel color of their roots ; lower surface of tail centrally solid hazel, pal- 
ing to ochraceous- tawny at base of tail, then a zone of black, and then an outer fringe of 
bright ochraceous-buff. The body side-stripes are sharply defined along their edges, 
but at their ends fade out gradually ; also the reddish of head blends by degrees w:ith 
colors of body adjacent. 

Color variations. — As far as we can see there is no difference in coloration 
between male and female, in spite of the extraordinarily bright pattern of coloration 
in this species. The young, even third-grown ones, are very similar to the adults in 
pattern, the difference consisting only in paler tones of color, especially about the 
head. There is, however, considerable change in the depth of coloration with season. 
In the spring and early summer the head region is much paler than in late summer 
and fall, and there is much other evidence of fading and wear to which the pelage 
has been subjected. In June specimens the head is pale cinnamon-buif. 

As far as we can determine from the collection of specimens studied there is but 
one thorough-going molt each year and this takes place in .Tune and July. The 
process is gradual. The exchange of old hair for new begins first on the head and 
progresses backwards ; but specimens often show a patchy coat, with areas of dense 
new hair on the head or back surrounded by old worn hair. 

We are unable to make out a distinguishable race from the Tr'nity Mountain 
region, trinitatis of Merriam, 1901, p. 126, type from "Trinity Mountains east of 
Hoopa Valley, California (altitude 5,700 feet)." The characters assigned, of color 
and size, are not borne out in our large series of specimens from the Trinity region 
as compared with series from the northern Sierra Nevada. There is, however, a 
slight tendency towards paling of colors in chrysodeirus at the southern end of the 
Sierra Nevada and along their east fiank ; for example, as shown by specimens from 
the east declivity of Kearsarge Pass, west of Independence. This modification is 
evidently in the direction of perpallidiis. 

Measurements. — Average and extreme measurements, in millimeters, of twenty 
full-grown specimens from the west slope of the high central Sierra Nevada are as 
follows: Ten males: total length, 272 (253-290) ; tail vertebra, 89 (75-104) ; hind 
foot, 41 (38-43) ; ear from crown, 15.7 (11.0-19.0) ; greatest length of skull, 44.0 
(42.2-46.2) ; zygomatic breadth, 26.6 (25.2-28.2) ; interorbital width, 10.4 (9.5-11.1). 
Ten females: total length, 266 (243-285) ; tail vertebrjE, 83 (67-100) ; hind foot, 
41 (39-44) ; ear from crown, 10.1 (13.0^21.0) ; greatest length of skull, 42.7 
(41.0-44.1) ; zygomatic breadth, 25.9 (25.0-27.1) ; interorbital width, 10.3 (9.2-11.0). 

It would appear from the above figures that in males the tail averages a little 
longer than in females. The skulls of old individuals, particularly males, relative age 
being estimated by degree of wear on the crowns of the molar teeth, show greatest 
size, particularly as regards zygomatic breadth and heaviness of rostrum. Old 
skulls also show wider brain-case, broader jugals, and stouter postorbital processes. . 

Weights. — Average and extreme weights, in grams, of twenty full-grown speci- 
mens from the west slope of the high central Sierra Nevada are as follows ; Ten 
males, 181 (155-218); ten females, 199 (136-245). Averages, in ounces : males, 
about 6J ; females, about 7. 

The heaviest example (245 grams) was a pregnant female. Males average heavier 
in the fall, when they are fat, than in early summer. 

Type locality.— Fort Klamath [mountains near], Klamath County, Oregon (Mer- 
riam, 1890, p. 10). 

Distribution area.- — Upper coniferous belt (Canadian and Hudsouian life-zones, 
less commonly down into Transition) along the Sierra Nevada, south as far as 
Cannell Meadows, in extreme southern Tulare County ; north through the Mount 
Lassen country to Mount Shasta, and thence west through the Trinity, Scott and 
Salmon Mountains (Mus. Vert. Zool.) to extreme eastern Humboldt County (Mer- 
riam, 1901, p. 126) ; also on the Siskiyou Mountains, along the Oregon border of 
western Siskiyou County (Merriam, 1901, p. 126); on the mountain mass' to the 



THE GROUND SQUIRRELS OP CALIFORNIA. 677 

• 
south of the Trinities, in the vicinity of Yolla Bolly Mountain, where Humboldt, 
Tehama and Mendocino counties adjoin ; and on the Warner Mountains, in eastern 
Modoc County (Mus. Vert. Zool.). The range of the Golden-mantled Ground Squir- 
rel in northern California is probably less continuous than indicated on the map 
(fig. 24), there being sequestered colonies on detached mountains along with similarly 
isolated representations of other boreal animals and plants. 

Altitudinally, this squirrel extends regularly to above timber-line, where the moun- 
tains are high enough for this, and downwards to the lower edge of the chinquapin belt, 
that is, scarcely as far as the yellow pines or Douglas firs. At the farthest south, in 
the Mount Whitney region, it has been noted as high as 11,800 feet, while downwards 
it was not seen below 7,000 feet. In the latitude of Yosemite, the highest point at 
which it was observed was 10,700 feet, and the lowest, Merced Grove of Big Trees, 
5,500 feet. In the Trinity region, the lowest occurrence noted was at 4,500 feet 
altitude. There is thus a notable lowering of altitudinal limits with increased latitude. 

Specimens examined. — A total of 259, from the following localities in California: 
Modoc County : ten miles northwest of Canby, 1 ; Sugar Hill, 11 ; Parker Creek and 
North Fork Parker Creek, Warner Mts., 9; Warren Peak, Warner Mts., 7; Dry 
Creek, Warner Mts., 1. Siskiyou County : head of Little Shasta River, northeast 
base Goose Nest Mt., 2; Mount Shasta, 10; Kangaroo Creek, 1; Wildcat Peak, 
3; Jackson Lake, 5; Saloon Creek Divide, 11; Castle Lake, 2; head of Rush 
Creek, G ; South Fork Salmon River, 8. Trinity County : Bear Creek, 11 ; North 
Fork Coffee Creek, 3 ; head of Grizzly Creek, 5 ; one-half mile south of South Yolla 
Bolly Mt., 3. Lassen County: Eagle Lake, 2; Horse Lake, 1. Tehama County: two 
to four miles south of South Yolla Bolly Mt., 19 ; Mount Lynn, 2. Plumas County : 
Mohawk, 1. Sierra County : near Sierraville, 1. Nevada County : Independence Lake, 
5. Placer County : Tahoe Valley, 2 ; Cisco, 13 ; two miles west of Soda Springs 
Station, 1. El Dorado County : Mount Tallac, 1. Mono County : Leevining Creek, 1 ; 
Walker Lake, 1 ; Bloody Canyon, 1. Tuolumne County : Ten Lakes, 1 ; Glen Aulin, 1 ; 
Tuolumne Meadows, 4 ; head of Lyell Canyon, 2 ; Aspen Valley, 2. Mariposa County : 
Vogelsang Lake, 1 ; Porcupine Flat, 3 ; one mile east of Merced Lake, 1 ; near Mono 
Meadows, 2 ; Mount Clark, 1 ; Merced Big Trees, 5 ; East Fork Indian Canyon, 1 ; 
Chinquapin, 3. Inyo County : Little Onion Valley, 1 ; Onion Valley, 4 ; Hockett 
Trail (near Carroll Creek), 2; Little Cottonwood Creek, 4; Cottonwood Lakes, 6. 
Fresno County : Kearsarge Pass, 5 ; Bullfi'og Lake, 8 ; Bubbs Creek, 1 ; Horse Corral 
Meadow, 2. Tulare County : Siberian Pass, 1 ; west slope Cirque Peak, 1 ; Whitney 
Creek, 3 ; Whitney Meadows, 13 ; west slope Olancha Peak, 1 ; Dry Meadows, 1 ; 
Monache Meadows, 7 ; Jackass Meadows, 14 ; Sirretta Meadows, 3 ; Cannell 
MeadowSj 5. 

Of all our ground squirrels the Golden-mantled is the most brilliantly 
colored. This rather bookish name for the animal is a translation of the 
scientific name of the species, chrysodeirus ; the more commonplace 
appellations locally employed, "Copperhead" or "Yellow-headed Chip- 
munk," serve just as well to set forth the conspicuous feature of 
coloration. Because of the bright colors and especially the striping of 
the body (see fig. 20d), this ground squirrel is often called "chipmunk;" 
but the latter name applies to a quite different group of animals which 
are slenderly built, agile, with long tails, and more numerous body 
stripes which involve the head as well as the body. 

The Golden-mantled Ground Squirrel is truly a ground squirrel in 
essential features of appearance and behavior as well as structure. 
Although it lives for the most part in forested regions, it keeps strictly 
on the ground when traveling or feeding, and only ascends rocks or 
logs when seeking a lookout station. The species, including its three 
subspecies in California, is confined to the higher mountains. One 
does not meet with it, in climbing the slopes, usually until well through 
the yellow-pine belt. Individuals begin to appear with the firs, and 
from there on to the upper limit of timber this species constitutes one 
of the most conspicuous features of the life of the forest floor. Here 



678 



THE MONTHLY BULLETIN. 




Fig. 24. Map showing California distribution of the golden-mantled and antelope 
groups of ground squirrels. The spots represent localities from which actual specimens 
have been examined. 

the animals are to be seen scurrying across open spaces to their burrows, 
just in front of the mouths of which they almost invariably stop a 
moment before plunging out of sight, displaying then to full advantage 
their color pattern. If the observer traverses their domain quietly, he 
may suddenly discover individual squirrels intensely observing him 
from perches on the tops of boulders or logs. There they sit in unosten- 
tatious, hunched-over postures, blending so well with the background 
that they are often passed by altogether unnoticed. The element pro- 
tecting them from observation most, at such times, seems to be their 
faculty for keeping absolutely still. 



THE GROUND SQUIRRELS OF CALIFORNIA. 679 

Rarely do Golden-mantled Ground Squirrels assume the upright 
picket-pin pose so characteristic of some others of the species. They 
most often maintain crouching attitudes when at rest. "When running, 
the gait is clumsy, as compared with the chipmunks usually to be seen 
close at hand. The tail is rather longer than in others of the smaller 
sized ground squirrels, and is more conspicuously displayed, often up 
over the back, or, when running, either held vertically or frisked 
violently fore and aft. This squirrel seems to be, as a rule, almost 
devoid of voice. As far as our own experience has gone, there is only 
a single chirp of alarm, not loud nor high-pitched, and even this is 
uttered but rarely. One observer (W. P. Taylor, MS) has been 
fortunate enough to run across a talkative individual. This animal was 
watched as it sat bolt upright on a log uttering a ''sharp call note, 
to-chick, sometimes varying this to tachack, p'r'r'r'r." A "general 
squirrel-like quality" was ascribed to these notes. At each utterance 
a violent flirt of the tail was given. 

Speaking of habitat again, the Golden-mantled Ground Squirrel 
shows decided preference for rocky slopes or forest floors littered with 
logs, but at the same time without heavy undergrowth. Open ground 
is preferred; yet it keeps out of large grassy meadows, save as visiting 
the margins of these where they adjoin the woods. Again we see adjust- 
ment so that each of the different kinds of rodents keeps to a separate 
forage area without undue waste of energy in competing with 
another. In the higher, rougher parts of the mountains we have often 
found the Copperheads inhabiting rock slides. Here, as in the other 
places, where there are logs or scattered rocks, the object appears to be 
to secure protection for their burrows, so that these can be located 
beneath heavy objects and thus prove difficult or impossible for badgers, 
coyotes or bears to dig out. 

The mouths of the burrows vary in diameter from 2 to 2^ inches, and 
the direction taken is usually steeply down into the ground for a foot 
or more. Unfortunately, we have never availed ourselves of an oppor- 
tunity to dig out the burrow system of a Golden-mantled Ground 
Squirrel. "We infer it to be simple and relatively short, for two reasons : 
the mounds at the mouths of the burrows are usually small in quantity 
of earth composing them ; and the big roots, logs or rocks beneath which 
the burrows in practically all cases lead, would seem to do away with 
the need of an extensive and deeply penetrating system so as to secure 
safety from enemies which pursue their prey by digging. 

The Golden-mantled Ground Squirrel is a spermophile in the truest 
sense of the word ; it is preeminently a gatherer and eater of seeds, and 
most of its time abovegrouncl seems to be occupied in diligent search 
for this sort of food. The cheek-pouches in this squirrel are developed 
to a maximum degree, and it is no uncommon thing to see an individual 
returning to its burrow from a foraging expedition with its two pouches 
so distended with seeds that the head seems double its ordinary width. 
We have counted 636 seeds from the two pouches of one squirrel. 

Some seeds identified in cheek-pouch contents saved are : Goose 
grass (Galium aparine), rice-root lily (Fritillaria sp.), pentstemon 
(Pentstemon azureus), and silver pine (Pinus monticola) . In the late 
summer and autumn months great activity is shown in garnering 
chinquapins, and there seems good reason to believe that large stor'es 

87 



680 THE MONTHLY BULLETIN. 

of these and various seeds are then housed away in the ground for use 
the following spring when the animals come out of hibernation and 
food is difficult to find otherwise. One individual had its cheek-pouches 
crammed with fragments of a brown-colored fungus such as forms 
bracket-like outgrowths on the bark of dead trees and old logs. Our 
experience shows this article of diet to be much sought after by members 
of the squirrel tribe generally. 

Then, too, the Golden-mantled Ground Squirrel eats meat, and even 
carrion, as we can testify from the persistency with which our meat- 
baited steel traps set for coyotes and other carnivores are sprung by 
the Copperheads. Indeed, it seems reasonable to infer that this ground 
squirrel would lose no opportunity to appropriate to its use the dead 
remains of any sort of animal. Around camp sites we have often 
received good evidence of the omnivorous nature of the Copperhead's 
diet from seeing them gathering the scattered barley from the ground 
where the horses had been fed and then gleaning the scraps of cooked 
meat as well as bread crumbs from our own table near by. In one 
case a ''Callo" came again and again to gnaw at a bacon rind. The 
young, but a third gro-wn, show almost as much industry in carrying 
away food as do the adults. 

That not all the food gathered, over and above what is immediately 
eaten, is carried to some definitely located storehouse, is shown by an 
observation by W. P. Taylor (MS). On the summit of Cloud's Rest, 
Yosemite Park, a "Callo" was encountered which was so used to the 
almost daily visits of people as to have become remarkably tame. It 
would run up to within three feet of a person, take the dried fruit 
thrown down for it, stuffing its cheek-pouches to capacity, and then run 
off just a little ways. After digging out a little hollow in the ground 
with its front feet, it placed the fruit therein and proceeded to cover 
it up with earth, using its front feet again. Sitting over the spot, it 
reached out to gather in additional loose stones until the cache was 
effectually concealed. Such hiding places as these are probably used 
only temporarily, at times when an abundance of food is suddenly 
available, to be stowed safely from someone else's reach as soon as 
possible, and later reclaimed for more permanent salvage. 

The young are born mostly in July, but as early as the last of June 
at the loweist altitudes of occurrence, and as late as the first week of 
August up near timber line. Young one-half grown were taken on 
Cannell Meadows, 7,500 feet altitude, Tulare County, on July 7, 1911 ; 
and young but a third grown were taken at Cottonwood Lakes, 11,000 
feet, near Mount Whitney, August 31, 1911. These dates are the 
extremes in the considerable series we have for time of appearance of 
young. Young come above ground when they are as small as one- 
fourth adult size (as determined by weighing). There is but one litter 
each year. This probably averages close to five in number. Six 
females captured along the central Sierras, of dates June 12 to 28, 
contained 5, 2, 5, 6, 6 and 5 embryos, respectively. The number of 
mammffi (represented by nipples) is either four pairs or five pairs, but 
this number is not, as some persons think, any index to the number of 
young born. 

The enemies of this squirrel probably include most of the carnivores 
of' the higher mountains. Hair of a "Callo" was found in the feces 



THE GROUND SQUIRRELS OP Cx\LIFORNIA. 681 

of a Mountain Coyote {Canis latrans testes) in the Yosemite National 
Park. Near Monaehe Meadows, in the Sierras of eastern Tulare County, 
one of the writers saw a Mountain Weasel {Mustela arkonensis) in 
full pursuit of a " Callo ' ' across open ground in the full sunshine of 
the bright forenoon of August 4, 1911. The squirrel was overtaken 
by the weasel, and what happened transpired so swiftly that no details 
were observable. A gunshot terminated the episode, and the "Callo" 
was found already stone dead, with two tooth-punctures on each side of 
the nape of its neck. 

The Golden-mantled Ground Squirrels hibernate regularly. They 
doubtless construct warm, dry nests underground, as individuals have 
been seen gathering soft materials and carrying these to their burrows. 
In one instance an individual was seen to pick up a piece of brown paper 
and after tearing it with its teeth and forepaws, stuff it into its cheeks 
and disappear into a burrow (C. L. Camp, MS). By the last of August 
these ground squirrels begin to acquire fat, and during September and 
October they are simply "rolling in butter," as the saying goes. This 
seems to be in preparation for their long period of dormancy, which 
extends from the last of October to the middle of April. 

Exact dates of going into, and coming out of, their winter sleep are 
not available to us. But in the Yosemite region in 1915 individuals 
were seen abroad in the Canadian life-zone commonly up to October 18 ; 
on October 30, in the same zone, but tw^o individuals were seen on the 
same ground where very many were noted a month previously; and 
none at all were seen on subsequent dates when they were looked for 
at suitable altitudes. The estimate of April 15 as near the time of 
reappearance in the spring is based on what we have been told by 
trappers and forest rangers, and their statements were only from 
memory. 

Since the territory inhabited by the Golden-mantled Ground Squirrel 
is practically altogether above the altitudinal limit of cultivation by 
man, this species rarely figures as anything worse than a camp-robber 
or "bummer" (see fig. 20d). We have heard packers complain of its 
proclivities in the way of carrying qff grain or provisions from summer 
camps in the higher mountains. But the total destruction of property 
thus wrought can hardly be formidable, and compensating for it to 
some degree must be counted the added animation lent to the mountain 
scene by the presence of these pleasing rodents. 



INYO GOLDEN-MANTLED GROUND SQUIRREL. 
Oallospermophilus chrysodeirus perpallidus Grinnell. 



Other names. — Sierra Goldeu-mantled Ground Squirrel, part; Yellow-headed Chip- 
munk, part; Callospermofhilus chrysodeiriis, part; Spermophilus chrysodeirus, part; 
Citelhis chrysodeirus, part. 

Field characters. — Exactly the same as for the Sierra Golden-mantled Ground 
Squirrel, save for pallor of coloration. 

Description. — Adult in fresh late-summer pelage : Pattern of coloration and chief 
features throughout preciselj' as in the Sierra Golden-mantled Ground Squirrel, but 
general tone of coloration paler ; middle of back, rump and sides tending towards 



682 THE MONTHLY BULLETIN. 

ashy, head less richly coppery, and under surface of body and upper surfaces of feet 
whiter ; under surface of tail medially ochraceous-tawny. Because the lighter colors 
are paler in tone, the jet black side-stripes stand out with greater sharpness than in 
the Sierran race. 

Color variations. — As in the Sierra Golden-mantled Ground Squirrel. In some 
specimens in fresh pelage the throat is pure white without a tinge of buff. Half- 
grown young just out of their nest-burrows show the characteristic paleness of their 
subspecies to as great a degree as adults in new coat. The pallidness of the adults 
in old worn breeding dress is greater in degree than in the Sierran race, evidently 
due to the greater bleaching effects of the more intense sunlight and dryness to which 
the Inyo animals are exposed. The innate paleness of the Inyo race is thus accentu- 
ated by external factors. 

Measurements. — Average and extreme measurements, in millimeters, of twenty full- 
grown specimens from the White Mountains, Mono and Inyo counties, are as follows : 
Ten males: total length, 26S (260-279) ; tail vertebrse, 92 (8(K105) ; hind foot, 40 
(38-43) ; ear from crown, 13.4 (11.0-15.0) ; greatest length of skull, 42.9 (42.0- 
44.0) ; zygomatic breadth, 26.2 (25.0^26.9) ; interorbital width, 10.0 (9.0-11.3). Ten 
females: total length, 264 (254-286); tail vertebrae, 85 (78-89); bind foot, 38 
(36-42) ; ear from crown, 13.3 (10.0^-16.0) ; greatest length of skull, 41.4 (39.6- 
42.3) ; zygomatic breadth, 25.9 (25.0-26.6) ; interorbital width, 9.8 (9.3-10.2). 

As will be seen from the above measurements in comparison with those given for 
the Sierran race, there are no important size differences between perpallidus and 
chrysodeirus; indeed it seems likely that, with large enough series, such discrepancies 
as are here in evidence would disappear altogether. The same variations due to age 
and sex seem to be present. 

Weights. — Average and extreme weights, in grams, of twenty full-grown specimens 
from the White Mountains, Mono and Inyo counties, are as follows : Ten males, 182 
(166.5-199.5) ; ten females, 160 (141.0-200.1). Averages, in ounces: males, about 
6i ; females, about 53. 

There were no gravid females in this lot. All were taken before August 10 and 
so none had become very fat. These facts may account for the lesser weights than 
shown for the Sierran race. 

Type locality. — White Mountains at 10,300 feet altitude, near Big Prospector 
Meadow, Mono County, California (Grinnell, 1918, p. 429). 

Distribution area. — The upper portions of the arid mountain ranges of extreme 
eastern California lying east and north of Owens Valley, namely the Inyo and White 
Mountains, and the mountain mass lying southeast of Mono Lake. Northernmost 
station. Mono Craters, Mono County (Mus. Vert. Zool.) ; southernmost, summit of 
Inyo Mountains east of Lone Pine (Elliot, 1904, p. 288). Along this extent of 
territory the distribution of the animal is^ not continuous but is interrupted at the 
lowermost gaps between the Inyo and White Mountains and at the extreme head of 
Owens Valley. Zonally, this race belongs to Boreal, but it extends down locally as 
low even as Upper Sonoran (see fig. 23). In other words, it extends from above tim- 
berline down to as low as 7,000 feet altitude (lower edge of pirions), the latter level 
for it being recorded from the bottom of Silver Canyon east of Laws. The highest 
observed station of occurrence is McAfee Meadow, 11,600 feet, near White Mountain 
Peak (Mus. Vert. Zool.). 

Specimens examined. — A total of 50, from the following localities in California: 
Mono County : Mono Mills, 4 ; Mono Craters, 1 ; McAfee Meadow, White Mts., 7 ; Big 
Prospector Meadow, White Mts., 22; Cottonwood '^reek. White Mts., 1, Inyo 
County : Roberts Ranch, Wyman Creek, White Mts., 2 ; Silver Canyon, White Mts., 4 ; 
Black Canyon, White Mts., 5 ; Mazourka Canyon, Inyo Mts., 4. 

This is simply a pale desert-range race of Golden-mantled Ground 
Squirrel, probably cut off but incompletely from its near relative, 
chrysodeirus, of the Sierra Nevada. There can hardly be expected to 
be any decided differences in habits between the two; yet the different 
"setting" of perpallidus — exceedingly dry, rocky slopes, with only 
sparse timber at best — has left in our minds an impression of distinct- 
ness. This only goes to show that we cannot conveniently, nor should 

90 



THE GROUND SQUIRRELS OP CALIFORNIA. 683 

we properly (from a scientific standpoint), consider any animal 
altogether apart from its normal surroundings. 

In the Inyo Mountains this squirrel Avas found by H. S. Swarth (MS) 
to range from the level of the lowest piiaons in Mazourka Canyon, about 
7,500 feet altitude, to the highest summit visited by him, 10,500 feet. 
In the White .Mountains, east of Laws, the senior author found it to 
range down Silver Canyon to as low as 7,000 feet altitude, and here 
this and the Antelope Ground Squirrel of the lower country overlapped 
in their ranges to a small degree. The "Callos," in such precipitous 
canyons as Silver Canyon,' were essentially "rock" squirrels, in that 
they had their retreats in the slides of shale rock at the bases of the 
cliffs and even in the broken rock outcrops far up the canyon walls. 
Through and along these they clambered, a bit clumsily perhaps, but 
without loss of foothold so far as was seen. 

Higher up, on the lofty rolling plateau forming the summit of this 
mountain range, the Golden-mantled Ground Squirrels were extremely 
abundant along the edges of the stunted forests of foxtail and lodgepole 
pines, and even far from timber out on the sagebrush flats, but in the 
latter locations there were always near at hand fractured granite out- 
crops which afforded safe retreats. Where there were grassy meadows 
the animals foraged all over them. It occurred to the observer that here 
in the White Mountains there was but this one species of ground squir- 
rel and that it therefore had the run of the whole place, as it were, 
without meeting with any competitor, as is the case in the Sierras and 
elsewhere. This would account for the facts as observed, namely, that 
in the White Mountains the Copperheads were extraordinarily abundant 
and ranged widely into all sorts of associations. 

Our lines of rat-traps baited with rolled oats brought in many 
"Callos," even youngsters but a third grown, and it was practically 
impossible to keep steel traps set during the day, as the bait, consisting 
of the bodies of the various birds and small mammals prepared f':'r 
specimens, seemed to be especially attractive to the squirrels. Wherever 
the traps were set, they would be searched out and unwittingly sprung 
as the squirrels scrambled over them in quest of the bait. It seemed 
impossible that the "Callos" could have located some of the settings 
except through scent, and it is reasonable to suppose that the sense of 
smell is employed not only in seeking meat but when searching for the 
bulbs of certain plants. 

Young were out in numbers the last week of July at the 10,000-foot 
level, being then one-third to one-half grown. Lower down, in Black 
Canyon at 8,000 feet altitude, half-grown young were seen on July 5 
(1917) ; and at 10,500 feet altitude, on Cottonwood Creek, third-grown 
young were noted on August 8. This shows the usual variation of 
appearance of young with altitude, which of course has to do with 
advance of the season, and so with temperature. 

In Mazourka Canyon, Inyo Mountains, two females, each containing 
six embryos, medium-sized and small, respectively, were taken May 19 
and 22 (1912). We found no evidence of litters of a larger number 
than six ; and there is certainly no more than one litter per year. 



684 THE MONTHLY BULLETIN. 

SAN BERNARDINO GOLDEN-MANTLED GROUND SQUIRREL. 
Callospermophilus chrysodeirus bernardiims (Merriam). 



other names. — San Bernardino Ground Squirrel; San Bernardino Spermophile ; 
Yellow-headed Chipmunk, part; Spermophilus hernardinus ; SpermopMlus chrysodeirus 
hrevicaudus ; Citellus chrysodeirus hernardimts; Callospermophilus bernardinus; 
Tamias chrysodeirus irevicaudiis; Tamias lateralis, part. 

Field characters. — ^The same as for the Sierra Golden-mantled Ground Squirrel. 
The slight shortness of tail characterizing this race is certainly not a sufficient differ- 
ence for notice at any distance. 

Description. — In all pelages : Coloration, as far as we can see after comparing large 
series of specimens, exactly as in the Sierra Golden-mantled Ground Squirrel. None 
of the paleness is apparent such as characterizes the Inyo race. 

Variations. — Of the same sort as discussed under the Sierran race. 

Measurements. — Average and extreme measurements, in millimeters, of twenty 
full-grown specimens from the San Bernardino Mountains are as follows : Ten males 
total length, 260 (240-278) ; tail vertebraj, 80 (68-90) ; hind foot, 40 (36-43) 
greatest length of skull, 43.5 (42.0-45.6) ; zygomatic breadth, 26.6 (25.5-27.6) 
interorbital width, 10.7 (10.1-11.3). Ten females: total length, 251 (236-271) 
tail vertebrae, 78 (72-86) ; hind foot, 38.5 (35-42) ; greatest length of skull, 41.8 
(40.4-43.0) ; zygomatic breadth, 25.5 (24.2-26.8) ; interorbital width, 10.2 (9.7-10.8). 

Unfortunately, ear measurements from fresh specimens are not available ; but dried 
skins look to have decidedly smaller ears than in either the Sierra f)r Inyo race, this 
character being especially noticeable in the young. It will be noted from the above 
measurements in comparison with those given for chrysodeirus and perpallidus, that 
the body size of hernardimis is just the same as in the others, while the tail length 
is decidedly less. This, then, is the character of the subspecies hernardinus , short- 
ness of tail ; and it shows up well in a series of specimens, even very young ones. 
However, this difference in tail length between adults of 'bernardinus and of chryso- 
deirus averages but somewhat less than half an inch, and individual variation brings 
overlapping in a certain proportion of specimens. In other words, an extra short- 
tailed chrysodeirus might even have a longer tail than an extra long tailed bernardinus. 
The race bernardinus is but slightly and incompletely differentiated. 

No weights are available for this subspecies. 

Type locality.— San Bernardino Peak, San Bernardino Mountains, San Bernar- 
dino County, California (Merriam, 1893, p. 134). 

Distribution. — Restricted to the relatively small area, not more than twenty-five 
miles in greatest width, comprised in the higher parts of the San Bernardino Moun- 
tains (see fig. 24). Belongs to the Boreal zone and upper part of the Transition. 
Extends up to the very summit of San Gorgonio Peak, 11,485 feet altitude, and 
down locally, as near Bear Lake, to 6,700 feet (Grinnell, 1908, p. 141). _^_____ 

Specimens examined. — A total of 84, from the following localities, all in San 
Bernardino County, California : San Gorgonio Peak, 2 ; Dry Lake, 3 ; South Fork of 
Santa Ana River, 14; Sugarloaf Mountain, 2; Bluff Lake, 61; Bear Valley, 2. 

Far separated by desert and lowland from the habitat of its near 
relative on the Sierras, the Golden-mantled Ground Squirrel of the San 
Bernardino Mountains has developed slight peculiarities which make it 
recognizable as a distinct race. It has the most restricted range, prob- 
ably, of any species or subspecies of ground squirrel in the state. It 
seems strange that it should be wholly lacking as an inhabitant of the 
San Gabriel and San Jacinto mountains, so near by on either 
hand and seemingly of quite similar environment to the San Ber- 
nardinos. On the higher parts of the San Bernardino Mountains it 
is certainly not on the wane, but thrives greatly, perhaps outnumbering 
all the other members of the squirrel family put together. 



THE GROUND SQUIRRELS OP CALIFORNIA. 



685 



In July, 1905, we found the Golden-mantled Ground Squirrels 
especially numerous around Bluff Lake, altitude 7,500 feet. Here they 
were to be seen all over the floor of the pine and fir woods, foraging 
among the chinquapin and deer-brush thickets. None was ever seen 
to climb a tree, though individuals were often seen perched motionless 
on stumps, logs or boulders. No matter where encountered, they always 
sought safety in holes in the ground or in crevices among rocks. They 
were notably quiet animals, giving only occasionally a single sharp note 
of alarm, or else, rarely, a low chuckle. 




Fig. 25. San Bernardino Golden-mantled Ground Squirrel as taken from nest while 
dormant during period of hibernation. Note that the animal is curled into an almost 
globular shape, with head down and nose snuggled against stomach between fore 
and hind feet ; tail curled underneath, partly concealing head. 

Around Bear Lake the Yellowheads were common through the woods 
down to the water's edge. On the north slopes of Sugarloaf, on 
August 22, they were very busy gathering cheek-pouchfuls of seeds of 
a lupine, and the fruits of the deer-brush {Ceanothus cordulatus) and 
of a recldish-fruited currant (Bihes sp.). Elsewhere they were seen 
carrying to their burrows quantities of the green burrs of the chin- 
quapin {Gastanopsis sempervirens) . The burrows usually opened out 
under logs, rotten stumps, or boulders. There was seldom any mound 
of earth to mark an entrance. 

A female squirrel captured at Dry Lake, 9,000 feet altitude, on 
June 22, was found to contain four embryos. The young must have 



686 TI-IE MONTHLY BULLETIN. 

been born generally during the early part of July, in a few eases as 
late as early August, to judge from the relative sizes of the young seen 
abroad. The first to appear aboveground were noted on July 17 at 
Bluff Lake. These were about one-third grown and seemed quite able 
to forage independently of their parent. The latter paid no attention 
whatever to them, only giving the sharp alarm note if an intruder was 
sighted. 

Two young ones trapped alive were taken home to Pasadena and kept 
in a cage. Early in the autumn one killed the other. The remaining 
individual survived for three years, latterly inhabiting a roek-pile in 
the yard and ranging freely where he would. Each winter he spent 
about seven months, October to April, inclusive, in hibernation (see 
fig. 25), with only occasional periods of activity for a day or two during 
spells of warm weather. It is interesting to note that this inclination 
to lie dormant was thus shown strongly at the low altitude of Pasadena, 
where the winter temperature scarcely ever reached the freezing point. 
There could have been no practical reason for it as regards failure of 
food, for a supply was alM^ays provided the animal in abundance. The 
annual program seems to require the dormant period, and this comes 
on at a regular time, and lasts the usual period, whether or not it 
happens to be essential to the survival of the individual. It is an 
inherited trait of the race. 



DESERT ANTELOPE GROUND SQUIRREL. 
Ammospermophilus leucurus leucurus (Merriam). 



PLATE V. 



other names. — Antelope Chipmunk, part ; Antelope Squirrel ; Harris Chipmunk ; 
White-tailed Spermophile ; Charming Spermophile ; Ammo ; Tamias harrisi; Epermo- 
philiis harrisnj Tamias leucurus; Gitellus leucurusj Spermopliilus leucurusj Citellus 
leucurus vinnulusj Citellus viniiulus; Ammospermophilus leueurus vinnulus. 

Field characters. — A small grayish brown ground squirrel with one white stripe on 
each side of body and with a short flat tail nearly always held cocked up over its 
rump so as to show the white under side conspicuously. Length of body alone about 
6 inches, tail about 2h inches more. 

Description. — Adult in winter pelage : General color effect on upper surface from 
nose to base of tail light brownish drab, changing on shoulders, flanks and outer 
sides of fore and hind legs to light pinkish cinnamon. Close inspection shows a 
grizzling, due to variegation of colors on the individual hairs, these being, on middle 
of back for example, plumbeous at extreme base, then pale gray, then black, then 
brown, iand finally white-tipped ; some of the hairs on sides and rump are longer than 
the average and black to ends. A sharply-defined narrow white stripe on each side 
of body from shoulder to side of rump. Eyelids white ; ears and sides of head bufEy 
white; whiskers black. Whole lower surface of body, from chin to root of tail, silvery 
white, the bases of the hairs lead-color. Soles of hind feet densely white haired 
forward to tubercles (see fig. 26a), thence to balls of toes naked, and plumbeous in 
color in dried specimens ; outer sides of hind feet and tops of fore feet tinged with 
pinkish cinnamon ; feet otherwise dull white ; claws blackish brown with pale horn- 
colored tips. Tail broadly haired and blunt-ended, narrowed at base ; above mixed 
black and white, giving an iron-gray effect, but, analyzed in its terminal half, an. 
outermost white border is seen to be preceded inwardly by a black band, then by a 
white band, then centrally by black; toward the root of the tail, above, there is a 
tinge of pinkish cinnamon, this overlaid with a grizzling as on the back. Under 





i 




THE GROUND SQUIRRELS OP CALIFORNIA. 



687 



surface of tail broadly pure creamy white, with au outer black border arouBd the 
terminal half, and succeeding this a white fringe. 

Adult iu summer pelage : Coat short and harsh instead of long and silky. General 
pattern of coloration as in winter, but tone of upper surface more buffy, especially 
so on top of head ; hairs on whole lower surface pure white to bases (no lead-color) ; 
tail as in winter. 

Color variations. — The sexes are alike in coloration. The young closely resemble 
summer adults save that the pelage is not so harsh. There is some individual varia- 
tion in tone of gray on back and in intensity of cinnamon on flanks and shoulders, 
but we are unable to find any correlation in these respects with locality. In other 
words, we are unable to find any tendency within the range of Ammospermopliilus 
leticurxis in California to form subspecies. The range of the animal is continuous 
from the Mexican border to the head of Owens Valley and there are no hindrances to 
continuous mixing of breed, such as seem essential to subspecific differentiation in 
other ground squirrels. 




Fig. 26. Feet of ground squirrels to show exient of hairing on soles and posi- 
tion and shape of tubercles, a. Desert Antelope Ground Squirrel ; 6, Stephens 
Soft-haired Ground Squirrel ; c, California Ground Squirrel. Natural size ; 
drawn from specimens. 

The two seasonal coats, winter and summer, are interchanged through a clearly 
defined procsss of molt. That from winter to summer begias as early as 
April 23 and continues in different individuals as late as June 18; that 
in the fall extends from September 12 to October 23. These dates are as 
shown by the specimens available. The spring molt commences on the forehead 
and proceeds backwards ; the last remnants of the winter coat are to be seen on 
the hind neck and rump. In the fall the order is reversed, and the rump first 
acquires the new winter pelage, the crown and forehead being the last areas to show 
the short harsh summer hairs. The hairs of the tail seem to be involved only in the 
fall molt, in other words they are not replaced in the spring when the rest of the 
pelage is. 

Wear, fading, and contact with alkaline soil bring about some modification in the 
tones of coloration. In some cases the tails are dirty light brown and the ends of the 
hairs are all curled up as if scorched by heat. In April specimens from the sand- 
dunes at the edge of Owens Lake near Keelei% the worn winter pelage shows a 
curious yellowish tone, but September examples from the same place, in process 
of molt, show the new winter pelage to be normal and exactly like that in specimens 
from Riverside County. 

We are unable to find any grounds for recognizing a separate race of leucurus 
from the Inyo region {vinnulus of Elliot, 1903, p. 241, type from Keeler, Inyo 
County). 

Measurements. — Average and extreme measurements, in millimeters, of twenty 
adult specimens from Inyo County are as follows : Ten males : total length. 21.", 
(200^235) ; tail vertebrae, 61.5 (50-70) ; hind foot, 37.7 (35-40) ; ear from crown, 
5.7 (5.0-7.0) ; greatest length of skull, 38.7 (37.5-40.6) ; zygomatic breadth, 22.3 
(21.5-23.1); interorbital width, 9.6 (9.4-10.1). Ten females: total length, 211 
(200-220) ; tail vertebrae, 57.7 (46.0-65.0) ; hind foot, 36.5 (35.0-38.0) ; ear from 
crown. 5.5 (4.0-8.0) ; greatest length of skull, 38.1 (37.1-39.4) ; zygomatic breadth, 
22.1 (20.6-22.9); interorbital width, 9.6 (8.9-9.9). 



95 



688 THE MONTHLY BULLETIN. 

Males seem to be a little larger than females, on an average, with proportionally 
longer tails. We are unable to find anything in our material to indicate variation 
in measurements with either altitude or latitude within the state of California. 

Weights. — Average and extreme weights, in grams, of twenty adult specimens 
from Inyo County are as follows: Ten males, 104.4 (94.5-120.7) ; ten females, 104 
(83.6-115.0). Average in ounces, for both males and females, about 3f. 

Type locality. — San Gorgonio Pass, below [east of] Banning, Riverside County, 
California (Merriam, 1889, p. 20; Stephens, 1906, p. 75). 

Distribution area. — In general, the southeastern desert region (see fig. 24). Life- 
zone chiefly Lower Sonoran, but extends locally up through Upper Sonoran and even 
into Transition (see fig. 2S). More specifically, the Colorado and Mohave Deserts 
(not, however, in some of the sandier or low-lying parts) from the Mexican line 
on the western rim of the Imperial Valley and the vicinity of Picacho on the 
lower Colorado River, north to the extreme head of Owens Valley in the vicinity 
of Benton, Mono County (Mus. Vert. ZooL). 

Along the western edge of the area inhabited by this squirrel, it extends well up 
onto the sides of the confining mountains and often far through the passes, as far as 
arid conditions prevail ; for example, in San Gorgonio Pass, Riverside County, above 
Cabezon, and over Walker and Kelso passes, in Kern County, down the valley of 
the South Fork of the Kern River to as far at least as Weldon (Mus. Vert. ZooL), 
thus well over the rim of the San Joaquin basin. There are in southern California 
at least two outlying colonies on the Pacific side of the desert divides ; namely, in 
San Jacinto Valley, Riverside County (Grinnell and Swarth, 1913, p. 326), and in 
Lytle Creek wash within six miles northwest of San Bernardino, in San Bernardino 
County (Mus. Vert. ZooL). 

Altitudinally, the species ranges from below sea-level, as at Furnace Creek Ranch, 
— 178 feet, in Death Valley, up regularljr to 6,000 feet on most of the desert moun- 
tains which reach that height, and in some instances to 7,500i feet, as at the north 
base of Sugarloaf in the San Bernardino Mountains (Grinnell, 1908, p. 141), and 
even to 8,500 feet, as near the head of Mazourka Canyon, in the Inyo Mountains 
(Swarth, MS). 

Specimens examined. — A total of 271, from the following localities in California. 
Mono County : Benton, and two miles south of Benton Station, 11. Inyo County : 
Laws, 6; Silver Canyon, White Mts., 9; Mazourka Canyon, Inyo Mts., 5; Independ- 
ence, and two miles north of Independence, 19 ; west base Kearsarge Pass, Sierra 
Nevada, 4; Lone Pine Creek, 4,500 ft., 10; Carroll Creek, 5,500 ft., and Hockett 
Trail, 6,500 ft, near Carroll Creek, 4 ; Keeler, 31 ; Olancha, 2; Darwin (fifteen miles, 
and two miles, north of), 7; Panamint Mts. (Emigrant, Wild Rose, Ilanaupah, and 
Johnson canyons), 17; Furnace Creek Ranch, and Triangle Spring, in Death 
Valley, 13 ; Shoshone, 2 ; Little Lake, 2. Kern County : Weldon, Onyx, and west 
slope Walker Pass, 16 ; one mile east of Warren Station, 1 ; Mohave, 12. Los Angeled 
County : Fairmont, 8. San Bernardino County : one mile northeast of Barstow, 1 ; 
Oro Grande, 2 ; mountains on west side of Colorado River, lat. 35°, 1 ; Blythe Junc- 
tion, 1 ; five miles below Needles, 1 ; opposite The Needles, 5 ; Chemehuevis Valley, 
2; Victorville, 14; San Bernardino Mts. (Cushenbury Springs, Cactus Flat, Doble, 
north base of Sugarloaf), 17; Cajon (Lytle Creek) Wash near San Bernardino, 1. 
Riverside County: base of San Jacinto Mts., near Cabezon, 7; Snow Creek, near 
Whitewater, 5 ; Vallevista, San Jacinto Valley, 4 ; Palm Springs, 7 ; Carrizo Creek 
and Dos Palmos Springs, Santa Rosa Mts., 5; Palm Canyon, San Jacinto Mts., 1; 
Riverside Mt., near Colorado River, 1. San Diego County : San Felipe Valley, 2 ; 
Grapevine Spring, 1; La Puerta, 2; Vallecito, 2; Jacumba, 1; Mountain Spring, 1. 
Imperial County : Colorado River, opposite Cibola, 2 ; twenty miles north of Picacho, 
4 ; eight miles east of Picacho, 2. 

The Antelope Ground Squirrels constitute a group distinct in many 
ways from all our other species. They are hardly less inhabitants of 
the ground, as compared with the tree squirrels and true chipmunks, 
but in manner they are more vivacious than any of the other ground 
squirrels ; they run at a much faster clip and hence can forage at greater 
distances from safety refuges. Their coloration is distinctive, too, 
gray, with one white stripe along each side of the back, and with the 

96 



THE GROUND SQUIRRELS OF CALIFORNIA. 689 

under side of the tail brilliantl)^ white. This latter feature is in itself 
unique, for it is accompanied by a most striking mannerism, that of the 
almost constant carriage of the stubby, flat-haired tail in an upright 
position, held against the back, so that the white under surface shows 
as a white ' ' flag ' ' when the animal is scurrying away, much as with the 
similarly advertising marks of the cottontail rabbit and antelope ; only 
with the ground squirrel the effect in catching the eye of the observer 
is still further heightened by the way in which it is spasmodically 
twitched whether the animal be at rest or running. This flickering 
beam of white ever holds the attention as long as the squirrel is below 
the level of the horizon, and short of its burroAV or the concealing tangle 
of prickly vegetation which it is so anxious to put between it and its 
pursuer. 

The race called appropriately Desert Antelope Ground Squirrel 
(locally, Antelope "Chipmunk" because of its stripes, small size and. 
sprightly manners) occurs broadly over the Colorado and Mohave 
deserts, thence north clear through the Inyo region. It shows rather 
wide adaptability to the varying conditions in this vast area, more so 
than any other desert ground squirrel, and ranges from below sea level, 
as on the floor of Death Valley, up regularly to 6,500 feet on the steep 
slopes of the desert mountains. It even "spills over" the confining rim 
of the Mohave Desert to the westward, locally, on to the Pacific drainage, 
as shown in detail in the accompanying list of specimens and on the 
map (fig. 24). Although notably continuous in its range over great 
stretches of country, it is not diificult to discover preferences, as indicated 
by relative abundance. Level sandy ground is, as a rule, but sparsely 
inhabited; and we know of some stretches of desert, such as the floor 
of the Coachella Valley northwest of Salton Sea, where none at all 
seem to exist, although the species is abundant in the foothills adjacent. 
The kind of ground most generally preferred seems to be hard-surfaced, 
gravelly wash-fans or hill slopes. Kinds of vegetation present seem to 
be immaterial, though clumps of squaw tea, creasote bush, cactus, or 
tree yucca characterize much of the territory where the Antelope 
Squirrels are most abundant. 

Our mention of the above preferences must not give an erroneous 
idea as to special nature of the habitat of this species. It may be said 
again, for emphasis, that this animal thrives in a great variety of 
situations. We have seen it on the mesquite-crowned sand dunes of 
Death Valley, there as a companion of the Death Valley Round-tailed 
Ground Squirrel; on the sagebrush covered flats at the extreme head 
of Owens Valley, in the metropolis of the Stephens Soft-haired Ground 
Squirrel; on the creasote hillsides near Little Lake, one of our very 
few record stations for the Mohave Ground Squirrel ; among the pinons 
and granite boulders of the northern section of the Panamint Moun- 
tains, then associated with the big Fisher Ground Squirrel; and even 
upon the steep rocky slopes of the White Mountains at 7,800 feet alti- 
tude, in the same rock slides with the Inyo Golden-mantled Ground 
Squirrel ! Truly a cosmopolite is the Antelope Ground Squirrel, just 
so far as the dry atmosphere of the desert extends ; but the coastal fog 
and general humidity of the Pacific drainage are almost strictly taboo. 

The burrow of this rodent is in nearly all cases situated at the side 
of a dense brush-clump or boulder so that protection is afforded from 

7— 4oC07 97 



690 THE MONTHLY BULLETIN. 

predators that dig, such as badgers and coyotes. The mouth of the 
burrow is kept open, and is flush with the surface of the ground ; and 
there is usually no trace of any mound. Sometimes there is a small 
pile of fresh earth adjacent to a hole, but this is subject to quick 
dissipation by the winds or the much more infrequent rains. The 
mouth of the burrow is subtriangular in outline, the flattish base of the 
triangle horizontal at the bottom. It is not often circular, as with 
pocket gophers and kangaroo rats, and usually can be recognized accord- 
ingly. There is evidence that these squirrels use the burrows of other 
rodents, too, such as those of wood rats, kangaroo rats, and even badgers. 
And in places where such retreats are afforded, individuals seem to 
have their headquarters in the interstices of rock slides. Suffice it to 
say that in the Antelope Ground Squirrel we do not find a good digger. 
It takes a temperamentally phlegmatic animal to dig effectively. The 
"Ammos" are too fidgety. 

This species does not live in colonies in the restricted sense in which 
this term should be used, but the burrows are scattered out pretty evenly 
over the general territory occupied. There is less of interdependence 
between the individuals of this species than in most other ground 
squirrels. 

In traveling through their domain one sees few of these ground 
squirrels as compared with their real numbers. They are adepts at 
dodging behind bushes, and at eluding observation by skipping off out 
of sight considerably in advance of the intruder. For example, in a 
census of animal life taken near Mohave, March 14, 1918, during a 
three-hour walk, but two Antelope Squirrels were seen, whereas six 
were found to have been caught in a line of rat-traps during the same 
length of time. Then, too, the characteristic tracks in the sand on a 
quiet day after it has been laid by a norther leave a graphic record of 
the multitudinous peregrinations of these active rodents. They can 
make more tracks in a given length of time than any other mammal with 
which we are acquainted! 

Some notes made by the senior author the second week of March, 
1918, near Mohave will help to give a clear idea of the characteristics 
of the animal under discussion. Nearly all individuals seen would run 
very fast across open spaces between the bushes, but would hesitate a 
moment or so when passing through the bushes. When approaching 
its burrow each animal would stop stock still just short of the mouth 
of the burrow, and watch the intruder intently with head turned to one 
side sufficiently so that it could look back past its rump. Meanwhile 
the tail was vibrated intermittently as usual. Presently the animal 
would dive down out of sight. One was seen to go down into a hole 
situated in the side of a mound of sand accumulated about the base of 
a very large creasote bush. This hole Avas one yard from the nearest 
upright stem, but was directed downward diagonally toward the root- 
system, and it was overshadowed by the radiating branches. The 
diameter of this burrow at its mouth was just 40 millim^eters (about 
one and three-fifths inches). The last that was seen of another squirrel 
as he dived for his burrow, he had his tail over his back twitching as 
violently as ever. He, too, had hesitated just an instant before the 
final plunge. 

08 



THE GROUND SQUIRRELS OF CALIFORNIA. 691 

One individual was surprised eight feet above tlie ground in a tree 
yucca, where he had doubtless been prospecting among the ripe pods 
for the seeds. He ran down the yucca trunk head foremost, with clearly 
audible noise of claws on rough bark. Even in this position the tail 
was kept appressed to the rump and was flicked in fore-and-aft direction. 
This ability to climb is not exceptional among individuals of this species, 
and is quite consistent with the general agilit}'- of the animal. Near 
Keeler, on the morning of September 25, 1917, six individuals were 
seen severally in the tops of sarcobatus bushes evidently gathering the 
small, fleshy leaves. At the distant approach of the observer each 
scurried to the ground and each had altogether disappeared by the 
time he had come up. At Onyx, Kern Countj^, June 21, 1911, one was 
seen perched on the top of a fencepost. At Carroll Creek, near Owens 
Lake, September 8, 1911, several were seen at different times perched 
bolt upright, picket-pin fashion, on isolated boulders out on the mesa. 

As a general thing Antelope Ground Squirrels do not have access to 
water and they live for long periods without it. Like other typically 
desert rodents, they can secure all the water needed in their systems by 
chemical elaboration of their food materials. Yet that water is sought 
for where available is shown by the following instances: When 
camped at a spring near the head of Kelso Valley, Kern County, July 
8, 1911, the senior author saw an ''Ammo" come without hesitation to 
the lowest hoofprints containing water below the spring and drink five 
times ; each time about ten seconds were apparently occupied in lapping. 
At intervals the animal looked around, vibrating his tail the while with 
great rapidity. At least six other individuals came to drink during 
that day, arriving through the brush from considerable distances. One 
of these, observed closely, was seen to lap hurriedly and briefly eight 
times. 

Some observations made at the same time and place bear further on 
the behavior of this species of ground squirrel. When one is stalked 
it wiU make a dash of ten feet or more to a near-by shrub or rock. If 
the observer continues to advance the squirrel disappears down a hole 
or under a bush, or else makes another similar dash and stops again. It 
then either stands on all fours with its back humped up toward the 
intruder and its head turned around so as to watch, or it stands 
upright on its haunches, turning more toward the observer. In either 
case the tail is held over the back and is wiggled, either antero- 
posteriorly or laterally. The tip of the tail, at least, shows no constant 
direction of movement. "When entering a burrow I saw one individual 
drop his tail down behind him and trail it into the burrow instead of 
carrying it over his back" (Storer, MS). Often when running an 
"Ammo" will be seen to jump short distances, quite clearing the ground. 
"I saw one in a tree yucca where I only came to detect his presence 
by seeing the shadow of his waggling tail ' ' ( Storer, MS ) . The animals 
seem to be able to climb the prickly cactuses and yuccas without 
sustaining any serious injury. 

The voice of the Antelope Squirrel is unique among the members of 
its tribe. It is not a "bark" at all; nor is it a "squeak." It may be 
described as a prolonged mellow rolling trill, weakening or falling in 
inflection toward the end. The tone is maintained on about the same 
moderately high pitch throughout, though an impression of lowering 

99 



692 THE MONTHLY BULLETIN. 

may be received because of the progressive diminution in volume. 
The sound is of a quality to carry well, yet even at very close range it 
rarely sounds loud. The direction of the performer is usually hard to 
fix. This shifting, ventriloquistic quality goes well with the shimmering 
landscape and elusive behavior of the animal, with which it is usually 
associated in our experience. 

The breeding season begins about the first of March and, in its various 
phases, lasts ordinarily until the end of May. At the highest altitudes 
the program is evidently retarded some because of the later advent of 
warm weather. There is nothing to indicate that more than one litter 
is produced each year by one female. The instances of late appear- 
ance of young (for exarhple, in August), where not accounted for by 
altitude, would seem likely to be due to individual variation in time 
of development of the reproductive instincts or else to abortion or early 
death of the first litter. The following is the more or less exact breeding 
data given in the field notes on file in the Museum of Vertebrate 
Zoology. 

The earliest date for embryos is February 20 (1910) near Needles 
on the Colorado River; the number of embryos was eight. On March 
11 (of the same year), in Chemehuevis Valley, south of Needles, a 
female was taken containing five embryos. The weather was yet cold, 
ice on standing water at night. It seems to be a rule with the squirrel 
family in the desert that the breeding season is so timed that the young 
of the year are well grown long before the period of intensest summer 
heat. 

March 11 to 16 (1918) thirty Antelope Squirrels were trapped or 
shot in the vicinity of Mohave. Of these, seventeen were males and 
thirteen were females, all adult and in breeding condition. The testes 
of the males were huge, measuring up to three-fourths of an inch in 
length. The uteri of the females were heavy- walled, but in only one 
case were there yet any embryos; one taken March 11 contained five 
well-developed embryos. The males were lean ; the females all more 
or less fat. On March 18 (1914) at Victorville two females were taken^ 
containing thirteen and fourteen embryos, respectively. On March 27 
(1907), at the same place, a female was found to contain eight embryos. 
On April 6 (1918), at Olancha, two females contained nine and ten 
embryos, respectively; and on April 12 one was found to contain seven 
embryos. On April 24 (1912) at Keeler a female was taken which 
contained six embryos. 

The average number of young per litter as figured from the above 
records of embryos is close to nine, with five and fourteen as extremes. 
Stephens (1906, p. 75) considers five to eight as the usual number. 
Nelson (1918, p. 443) gives four to twelve. Mearns (1907, p. 301) 
records that near Mountain Spring, in May, 1894, ten small young of 
uniform size were caught from one hole. 

The mammfB are generally in five pairs, occasionally in six, rarely 
five on one side and six on the other. 

The earliest date we have for the appearance of young aboveground 
is April 23 (1917) at Furnace Creek Ranch, Death Valley; one young- 
ster scarcely one-fifth grown (its weight was but 17.7 grams) was found 
wandering about weakly under a mesquite (see fig. 27). The next date 
is May 13 (1908) for third-grown young at Cabezon, and records for 



THE GROUND SQUIRRELS OP CALIFORNIA. 



693 



the last week of May are numerous. The latest date is September 4 
(1908) for half -grown young at Yallevista, San Jacinto Valley. From 
all the facts at hand we would estimate the usual date of birth for this 
species to be close to May 10. 

By the time they are half grown the young seem to be well able to 
forage for food by themselves. No solicitude has been observed on the 
part of the parent. The young show themselves to be less shy than 
adults, and for this reason it is probable that a large toll is taken by 
their enemies during early summer, until the young get sophisticated. 

The Antelope Ground Squirrel, according to the data above given, 
is the most prolific of all our species of ground squirrels. It can be 
inferred from this that existence on the desert, in the mode followed 




Fig. 27. Desert Antelope Ground Squirrel, about one-flfth grown, found wandering 
about weakly under a mesquite at Furnace Creek Ranch in Death Valley, April 23, 
1917. Photographed by J. Dixon. Although very young and feeble this little squirrel 
persisted in holding its tail at all times over its back in characteristic Ammospermo- 
philus fashion. 

by this squirrel, is the most precarious. The factor of high mortality 
must therefore be provided against by high birth rate. The category 
of predaceous animals which occupy the, same territory and which are 
sure to prey habitually upon the Antelope Squirrel includes ''snakes, 
weasels, foxes, coyotes, badgers, bobcats, and many kinds of hawks" 
(Nelson, 1918, p. 443). 

At all the lower elevations, where the winters are not especially cold, 
Antelope Ground Squirrels are to be seen abroad at all seasons. For 
instance, around Victorville in December and January, 1904-05, and 
at Palm Springs in December, 1904, they were to be seen nearly every 
day, though they did not seem to be foraging far and wide actively 
then as is their wont in March and later. At the former locality on the 
coldest windy days none was seen. It is very likely that at higher 
places, altitudinally, especially where there is some snow, as at the head 
of Owens Valley, these animals hibernate through the coldest months. 



101 



694 THE MONTHLY BULLETIN. 

The fact that there is a special winter pelage, long, full and silky, would 
seem to have some meaning as an accompaniment of outdoor activity 
at that season. Certain it is, that in texture, the pelage of the Antelope 
Squirrels is quite different from that of those species which hibernate 
regularly and long. The latter are woolly, with much under-fur. In 
the fall and winter ' ' Amnios ' ' are uniformly very fat. This condition is 
probably maintained by drawing upon their food stores, which, to 
judge from their persistent industry earlier in the season, must be 
extensive. We have never taken the opportunity to dig out the burrows 
to see how the seeds and other foodstuffs are garnered. Interesting 
facts doubtless await inquiry in this direction. 

The Antelope Ground Squirrel is preeminently a gatherer of seeds 
and fruits. The two inside-opening cheek-pouches are extensive, doubt- 
less on this account. Rarely does an animal captured away from its 
burrow fail to show something in them. The following records of 
findings of this nature will give a good idea of the diet of the species. 

In the tree-yucca belt near Mohave, March 11 to 16, 1918, many of 
the squirrels examined were carrying the large flat black seeds of the 
tree-yucca (Yucca hrevifolia) . These seeds were being gathered for 
the most part from the ground, where they had fallen from the pod- 
clusters overhead. But in a few cases the squirrels were seen up in the 
yuccas going right after the ripe pods themselves. The greatest number 
of these seeds being carried at one time was seventeen, this in the case 
of a male taken on Lee Flat, fifteen miles north of Darwin, September 
28, 1917. A female taken in Walker Pass, June 27, 1911, contained in 
its cheek-pouches 98 shelled seeds of juniper {Juniperus calif ornicus) . 
A female captured at Keeler, April 28, 1912, had gathered into her 
cheek-pouches 178 husked seeds of the salt-grass (DisticJiUs spicata). 

Cactus seeds are frequently gathered, and, in season, the fleshy fruits 
are eaten. At Vallevista, San Jacinto Valley, September 4, 1908, the 
squirrels were feeding chiefly on the ripe. cactus "pears." The animals 
were well stained with the purple juice both outside and in; the whole, 
abdominal region was purple in some of the individuals skinned for "* 
specimens. At Cabezon, May 6, 1908, a squirrel was watched in the 
top of a cholla cactus eating the tender new-growth buds. The animal 
seemed to be able to move about without its feet being injured by the 
spines, but upon being shot a thorn was found sticking firmly in the 
roof of its mouth. 

This squirrel also gathers, doubtless for food, the stems of squaw-tea 
(Ephedra) , cut into sections, and the leaves of Sarcohatus. Immedi- 
ately after rains, when the evanescent annual vegetation of the desert 
starts to grow, sprouting plants of certain species are also gathered. 

Judging from the frequency with which Antelope Ground Squirrels 
get into meat-baited traps, they must have a decided taste for flesh. We 
have also frequently found them eating into the bodies of rodents already 
caught and killed in small traps, and in one case, at least, one of its 
own kind was the victim. Nelson (1918, p. 443) says that insects are 
eaten when occasion offers. 

As for cultivated crops, it is not often that Antelope Ground Squirrels 
are to be found in settled regions, and even where they are, they do not 
seem to be attracted by the conditions which accompany irrigation. 
For example, around Cabezon in San Gorgonio Pass, in May, 1908, the 



THE GROUND SQUIRREI^S OF CALIFORNIA. 695 

farmers and oreliardists reported that little or no damage was done by 
this rodent, although the big Fisher Ground Squirrel was a decided 
pest there. The little Antelope "Chipmunks" seemed to keep closely 
to the wild land, feeding upon the native seeds and fruits, especially 
those of the cactuses. 

Still, locally, they may prove noticeably destructive. This was the 
case in an almond orchard near Fairmont in northern Los Angeles 
County, where in June, 1904, the present authors saw the animals 
climbing the trees in the outer rows next to the wild land and carrying 
down the as yet unripe almonds. These and the Fisher Ground Squir- 
rels were both complained of bitterly by the owner. Again, in Owens 
Valley near Independence, on May 7, 1912, a male Antelope Ground 
Sqjiirrel was captured, with its cheek-pouches filled with wheat. The 
nearest grain field was a quarter of a mile distant. It is thus quite to 
be expected that where cultivated land adjoins wild land this species 
will make raids upon such crops as prove to its liking. 



NELSON ANTELOPE GROUND SQUIRREL. 
Ammospermophilus nelsoni nelsoni (Merriam) 



Other names. — Nelson Spermophile ; Nelson Ground Squirrel ; Antelope Chipmunk, 
part; Spermopliilus nelsoni; Citellus nelsoni. 

Field characters. — A small yellowish-brown ground squirrel with one narrow white 
stripe on each side of body, and with a short fiat tail nearly always held curled up 
over the rump so as to show the creamy white under side. Length of body alone 
about Q-} inches, tail about 2-1 '-jches more. 

Description. — Adult in summer pelage: General color of upper surface from nose 
to base of ta'l light clay color, brightening toward pinkish cinnamon on shoulders, 
flanks, and outer sides of fore and hind limbs ; a narrow white stripe on each side 
of body from shoulder to side of rump. Eyelids, ears and sides of head dull buffy 
white ; whiskers black. Whole lower surface of body white, the hairs white to 
bases ; soles of feet densely white-haired forward to tubercles, thence to balls of toes 
naked ; upper surfaces of feet white, buff tinged ; claws blackish brown with pale 
horn-colored tips. Tail as in leucurvs. but upper side near base clay color ; under 
surface creamy or buffy white centrally. Adult in winter pelage : Goat softer, the 
hairs being longer and more silky than in summer. General coloration as in summer, 
but tone of upper surface a little darker, and with a fine grizzling due to more 
variegated color pattern on the individual hairs. White hairs of lower surface with 
extreme bases lead-color. 

Color variations. — -Sexes alike, as far as we can see. Young colored as in the 
summer adults, but pelage finer in texture. 

Measurements. — Average and extreme measurements, in millimeters, of twenty 
full-grown specimens from the vicinity of Bakersfield, Kern County, are as follows : 
Ten males: total length, 226 (210-242) ; tail vertebrse, 70 (61-76) ; h"nd foot, 38.6 
(36-40) ; ear from crown, 5.3 (5-6) ; greatest length of skull, 39.9 (89.0-41.6) ; 
zygomatic breadth, 23.2 (21.4-25.0); interorbital width, 9.9. (9.5-10.4). Ten 
females: total length, 221 (203-238); tail vertebrae, 68 (64-74); h-"nd foot, 3S.4 
(35.0-41.0) ; ear from crown, 5.7 (5.0^6.0) ; greatest length of skull, 39.4 (37.8- 
41.3) ; zygomatic breadth, 22.6 (21.5-24.4) ; interorbital width, 9.7 (9.0-10.6). 

Males will be seen from the above figures to average slightly larger than females. 
The decidedly greater size of nelsoni as compared with leucurus is at once apparent. 

Weights. — Three adult females were found to weigh 141.S, 142.6, and 179.0 grams, 
respectively; average, 154.5 grams, or 54 ounces. In bulk nelsoni is thus about 
50 per cent larger than leucurus. 

103 



696 THE MONTHLY BULLETIN. 

Type locality.— Tiptou, Tulare County, California (Merriam, 1S93, p. 129). 

Distribution. — Occupies the floor of the southern end of the San Joaquin Valley, 
and adjacent arid hills and included vallej^s immediately to the westward (see fig. 24). 
Life-zone Lower Sonoran. More specifically, extends from vicinity of Bakersfield 
(S miles northeast) and Poso, in central Kern County, west to the Carrizo Plains 
and Cuyama Valley, in southeastern San Luis Obispo County, south to the mouth 
of San Emigdio Creek, 12 miles due east of Maricopa, Kern County, and north to 
Huron, Fresno County, and Tipton, Tulare County. 

Specimens examined. — A total of 43, from the following localities in California. 
Kern County : eight miles northeast of Bakersfield, 32 ; twelve miles due east of 
Maricopa, 5 ; McKittrick, 3. San Luis Obispo County : Carrizo Plains, 3. 

The Nelson Antelope Ground Squirrel is called Antelope Chipmunk 
by many of the people who live in the southern San Joaquin Valley. 
No distinction is made by them between the present species and the 
Antelope Squirrel of the Mohave and Colorado deserts. This is not 
surprising when we consider the rather close general resemblance 
between the two. When specimens of the two animals are in hand, 
tone of coloration alone suffices for distinguishing them. The ground 
color of the Nelson Squirrel is distinctly clay color, while that of the 
Desert Antelope Ground Squirrel is pinkish buff. In the former, too, 
the under side of the tail is crearay buff, while in the latter it is pure 
white. In bulk the Nelson is approximately 50 per cent the larger. 

The Tehachapi Mountains on the south and the Greenhorn Mountains 
to the east help to form a continuous barrier between the range of 
these two near-related squirrels. We find the Nelson Squirrel to be 
restricted for the most part to the Lower Sonoran life-zone in that 
portion of the San Joaquin Valley which lies south of Tulare Lake. 
It is notably numerous in the oil districts. The Nelson Squirrel may 
be distinguished from all other rodents that occur in this region by 
having a very short, flat-haired tail (less than 3 inches in length) and 
by the presence of a single white stripe on each side of the body. The 
name borne by this species was given to it by its original degcriber 
(Merriam, 1893, p. 129) as a recognition of the contributions to mam- 
malogy of Edward W. Nelson, now chief of the United States Bureau 
of Biological Survey. 

During the rainy season many of the smaller streams in the southern 
and western foothills around the San Joaquin Valley cut deep and nar- 
row channels, but when the flood waters of such streams reach the upper 
plains of the great valley their course is marked by broad washes with 
low, perpendicular banks. The silt-bearing waters finally spread out, 
forming broad, alluvial fans, and often sink into the thirsty soil before 
they reach the lower alkaline plains. The lower reaches of such stream 
courses, dry and desertlike most of the year, are the preferred haunts 
of the Nelson Ground Squirrel. Here burroAvs are easily dug between 
the hard layers of the stratified banks of the washes, affording safe 
retreats from such predators as the coyote and badger. A luxurious 
though brief -lived growth of vegetation results from the thorough 
natural irrigation of the rich soil of the alluvial fans and the squirrels 
are thus afforded an abundant food supply the rest of the year. Indi- 
viduals and even colonies are to be found along the little gullies and 
ridges of the upper slopes between the mouths of the streams and the 
foothills, while a few may be found along the edges of the alkali ground 



THE GROUND SQUIRRELS OP CALIFORNIA. 697 

of the lower levels; but the metropolis of the species is in the middle 
region among the salt-bushes (Atriplex) which thickly dot these plains. 

This ground squirrel is soon driven out when fields come under 
cultivation. It clings closely to the wild land and apparently rarely 
if ever invades adjoining ground which may happen to be under culti- 
vation. Thus in May, 1918, at the mouth of San Emigdio Creek, Kern 
County, we found these squirrels quite abundant on three sides of an 
extensive alfalfa field which was entirely surrounded by virgin tracts 
of the salt-bush (Atriplex) , yet during our stay of nearly two weeks, 
not a single Nelson Squirrel was observed to enter this field or even to 
touch, a leaf of the alfalfa. 

As usually encountered, the Nelson Squirrels are seen scurrying 
rapidly across open places between clumps of salt-bushes, or else, more 
rarely, standing straight up to their full height in true "picket-pin" 
fashion just before they disappear down their burrows. The normal 
mode of travel is by a series of short rapid jumps of from 6 to 12 
inches. When approaching a hole leisurely, or when foraging about, 
the animals sometimes slow down into a walk. 

These squirrels are not early risers, being rarely found abroad until 
well after sun-up. At the mouth of San Emigdio Creek, during the 
second week in May, Nelson Squirrels began to appear at the entrances 
to their burrows in the south-facing overhanging bank of a wash, 
between 8 and 8 :15 in the morning. They appeared earlier in the day 
at this point than elsewhere in the vicinity, doubtless because this bank 
first received the full force of the early morning sun. Ten o'clock 
marked the period of greatest activity. The squirrels under observation 
disappeared each day between 11 :30 and 12 o 'clock and were rarely 
seen again until 2 :30 in the afternoon, when they began to reappear in 
the shade of certain dense-foliaged salt-bushes that grew on the brink 
of the wash. Although they were frequently seen to bask in the rays of 
the early morning sunshine, these squirrels shunned the direct sunlight 
at noonday. As early even as 10 o'clock in the morning one female 
was seen repeatedly to seek shelter in the shade of a fencepost (J. 
Dixon, MS). 

The tail of the Nelson Antelope Squirrel, as with the Desert Antelope 
Squirrel, is the most conspicuous feature about the animal. When 
running, the tail is curved forward over the back, in which position the 
creamy under surface is most effectively displayed so that at a distance 
one receives the impression that merely a bit of thistledown is blowing 
along over the sand. The body of the animal, with its ground-like ton(i 
of color, practically disappears. This illusion is furthered by the 
twitching of the tail and by the momentary pauses of the animal which 
correspond closely with the usual interrupted flight of a tuft of thistle- 
down. 

When the squirrel is foraging about on all four legs, or else sitting 
up, the tail is held curved forward over the back; in fact, one rarely 
sees the tail held in any other position (see fig. 28) . At such times the 
tip of the tail is often curved slightly upward or outward. When 
excited or frightened the tail of the animal is twitched rapidly fore and 
aft, but rarely or never sideways. One individual observed at a dis- 
tance of ten feet was seen to vibrate its tail intermittently with exceeding 
rapidity, there being half-minute intervals between the periods of 

105 



698 THE MONTHLY BULLETIN, 

vibration. There were from four to six of these periods of vibration 
in a series. The tip of the tail would travel only a short distance, less 
than a couple of inches, as it was never seen to reach a vertical position 
above the animal's back when the squirrel was standing on all fours. 
These squirrels are notably cautious about coming out of their holes ; 
they were never seen to come out hastily. First the nose and then the 
eye of an animal would stealthily appear, and then a thorough look 
around for possible danger taken, before a squirrel considered it safe 
to leave the shelter of its burrow. However, when they do move, their 
actions are very sudden, as though they had been undecided just what 
to do, but having once made up their minds are off in a whirl of dust. 
These rodents are more easily alarmed by sound than by sight. The 



Fig. 28. Young Nelson Antelope Ground Squirrel, photographed by J. Dixon, May 
9, 1918, on lower San Emigdio Creek, Kern County. Note how well the general color 
of the animal blends with the tone of the background, and yet how strikingly the white 
of the under side of the tail shines forth. 

cracking of a twig would send them hot-footed to their burrows. Yet 
the observer was able to walk up to within thirty feet of them in plain 
sight in the open as long as he made no violent motions. By approach- 
ing slowly and directly towards the squirrels, it was frequently possible 
to get within ten feet when they were sunning themselves at the 
entrances to the burrows under the overhanging banks. 

The sense of smell seems to be extensively used in the daily life of 
these animals. At the close approach of the observer the noses of these 
little squirrels were seen to twitch constantly as if in effort to catch the 
scent of the stranger. The sense of smell also plays an important part 
in locating food. Then again it is used socially. When following each 
other about, in and out of the burrows, they often stop and sniff to see 

106 



THE GROUND SQUIRRELS OF CALIFORNIA. 



699 



which way the other has gone. Smell serves as a means of identifying 
the other members of the same family. Outsiders are quickly detected 
and promptly driven away. The members of one family of squirrels 
which was closely watched were found to be very sociable, never quarrel- 
ing among themselves. The parents were often seen sitting side by side 
feeding in perfect harmony (see fig. 29), while at other times this pair 
would sit together and rub noses in a very affectionate way. The only 
time that they were seen to show fight was when a strange male squirrel 
attempted to enter their burrow, and then the male of the pair promptly 
put the intruder to flight. 




Fig. 29. Adult male and female Nelson Antelope Groimd Squirrels, feeding in 
iiarmony side by side under wholly natural conditions. Photographed by J. Dixon, 
May 9, 1918, on lower San Emigdio Creek, Kern County. The openings under the 
horizontal layers of the wash banks afforded these squirrels safe retreats. Note the 
characteristic Ammospermophilus pose of body and tail. 

The alarm note of the Nelson Antelope Ground Squirrel is much 
subdued as compared with the clear penetrating trill of the Desert 
Antelope Ground Sqairrel. In fact, the former is much less frequently 
heard at all. "While the junior author was watching a family of Nelson 
Squirrels at play on the morning of May 8, 1918, an old female was seen 
to disappear into one of the numerous holes in the bank. About two 
minutes later his attention was attracted by the low, inquisitive chirr 
of this same squirrel, which was standing motionless less than ten feet 
behind him. This alarm note was repeated five or six times at intervals 
of from 30 to 45 seconds. In uttering this note the mouth was opened, 
but the effort was not convulsive nor was the thorax greatly contracted. 
The note was subdued in tone and probably not audible to human ears 
at a distance exceeding one hundred feet. The confidential quality of 
the call note reminded the observer very much of the clucking note of 
the female valley quail when keeping her young together. 



107 



700 THE MONTHLY BULLETIN. 

Numerous holes in the sides of gullies and in the banks of washes 
form the most conspicuous signs of the presence of the Nelson Squirrel. 
Tracks and mounds at the entrances to burrows are not as noticeable 
as one would expect from the number and size of the animals. Trails 
from the burrows to the feeding grounds of this species are usually not 
well defined. In one place near the mouth of San Emigdio Creek 
these squirrels were obliged to cross a large dusty area in traveling 
back and forth between their burrows and their feeding grounds. 
Numerous tracks in this dusty spot showed that the squirrels in this 
colony did not follow definite trails, but that each individual chose his 
own route. In passing around a projecting bank, however, the tracks 
were found to converge for a short distance into broad, well-beaten 
paths six to eight inches wide. 

The favorite location for burroAvs of this squirrel is, as already stated, 
in the sides of banks at the edges of washes or gullies. The burrows 
usually enter near the bottom of the bank. The entrances to the 
burrows vary from 1^ to 8 inches in diameter. The largest holes 
are in soft ground beneath horizontal hard strata in the bank and their 
large diameter is due at least in part to the weathering or caving in of 
the soft earth. The burrows of smallest diameter are found in hard, 
level ground at the roots of Atriplex bushes. The entrances to burrows 
in the banks are from six inches to fifty feet apart. These bank burrows 
run back in a generally horizontal direction and are interconnected to a 
considerable extent under the bank. This was proven by seeing a certain 
squirrel, known by sight to the observer, disappear into one hole and 
then in a few minutes reappear at the mouth of an a-d joining burrow 
twenty or more feet distant. 

All of the eight burrows dug into by various persons from this 
museum have proven to be simply refuge burrows, with only one 
entrance ; that is, not of the intercommunicating type. Squirrels were 
found to reappear in from 5 to 15 minutes after they were chased into 
such burrows. These refuge burrows were found to be short, less than 
twelve feet in length; shallow, less than three feet in depth; and of 
small size, less than two inches in diameter. In three cases the squirrels 
were gassed in these burrows and an hour later dug out. Two of the 
animals were found dead near the wasteball at the entrance of the 
burrow, where they had evidently been overcome by the gas when 
attempting to make their way out. 

No nests were found in any of the burrows that were dug out, although 
nesting burrows were particularly sought for. Consequently we have 
no information to offer regarding this phase of the animal 's life history. 

The Nelson Squirrels found near the mouth of San Emigdio Creek 
were found to be moderately infested with fleas. The squirrels were 
often seen to stretch out to their full length and roll over and wallow 
about in the fine powdery alkaline dust which in many places was an 
inch deep under the overhanging banks along the edges of the washes. 
Such dust baths, which were frequently indulged in with considerable 
evident satisfaction by the squirrels, are likely to serve in keeping the 
pelage of the animal clean as well as to discourage the fleas. 

Our data regarding the breeding of AmmospermopMlus nelsoni is 
scanty. The breeding season appears to be much earlier in this species 
than in the case of the Fisher G-round Squirrel in the same region. 

108 



THE GROUND SQUIRRELS OF CALIFORNIA. 701 

The young of nelsoni are apparently all born before the last of April. 
None of the numerous females taken in the vicinity of Bakersfield 
between April 27 and May 12 were found to contain embryos. A male 
one-fourth gro^vn was taken eight miles northeast of Bakersfield on 
May 7j 1911, and a half -grown young one was taken at McKittrick on 
May 18, 1911. On May 9, 1918, two immature individuals, weighing 
100 and 103.3 grams, respectively, were taken at the mouth of San 
Emigdio Creek. These, male and female, were thus over two-thirds 
grown and were at this time foraging for themselves. These two 
youngsters were extremely playful and on several occasions they were 
seen to stand upon their hind legs and with their front paws braced 
against one another's shoulders they wrestled and pushed each other 
about energetically. The parents of these young squirrels had evidently 
east them off to shift for themselves. 

Because the California and Fisher Ground Squirrels have -increased 
and profited by the farming activities of man in parts of the San 
Joaquin Valley, it has been suggested that possibly this increase has 
tended to crowd out AmmospermopMlus nelsoni and therefore restrict 
the range of the latter (Taylor, 1916, p. 20). At the mouth of San 
Emigdio Creek both nelsoni and fisheri were found in numbers. Old 
colonies of fisheri, as shown by their extensive workings, were found 
between colonies of nelsoni. The Antelope Squirrels occupied the 
sandy washes and the areas covered by the salt-bush, while the Digger 
Squirrels occupied the more open tracts which were covered by a low 
growth of foxtail. While there must be a certain degree of competition 
as regards food supply between the two kinds of squirrels, this com- 
petition is probably no greater than that which exists between the 
Nelson Antelope Ground Squirrel and, for example, each of the two 
species of kangaroo rats which forage at night for similar food over 
the same ground used by the Nelson Squirrels in the daytime. We 
found no evidence, in this case, that the Digger Squirrels were driving 
out the Antelope Squirrels. 

The badger is one of the chief enemies of the Nelson Ground Squirrel. 
Many squirrel burrows were found that had been dug out by this animal, 
and, since in their refuge burrows these squirrels have no back door 
of escape, capture in such cases must be more or less certain. 

On May 19, 1918, a pair of Nelson Squirrels was observed to remain 
out in the open and watch a pair of Golden Eagles go through a series 
of aerial evolutions overhead, in which, with talons tightly locked 
together, the birds looped the loop three times. The eagles were 
obviously seen by the squirrels, and the swish of their wings was 
plainly heard by the observer, yet the squirrels were not in the least 
alarmed. However, when a Red-tailed Hawk flew over, the squirrels 
hustled at once into their holes. It was therefore inferred that the 
hawks and not the eagles were the active enemies of these small squir- 
rels. Coyotes and kit foxes also dig out the squirrels in their burrows 
and probably pounce upon a few individuals during the daytime. 

In foraging, these squirrels slip along close to the ground, often 
stopping in the shelter of a bush or pausing in the open and searching 
quietly, with body extended, for small seeds upon which they feed. On 
May 6, 1918, an old female which was nursing young was observed for 
several minutes at a distance of fifty feet. During this time the squirrel 
stood at her full height with body erect, busily munching a green head 



702 THE MONTHLY BULLETIN. 

of alfilaria and keeping a careful watch at the same time upon the 
intruder. A few days later a squirrel of this species was seen gathering 
dry seeds of the alfilaria. It is difficult in the field to be sure just what 
kind of seeds the squirrels are seeking out, since the seeds are too small 
to be seen at any great distance even with the aid of binoculars, and 
the stomach contents are so finely chewed that it is impracticable to 
identify the food constituents. 

On one occasion an individual was seen to eat the dried flesh from 
the hind leg of a dead kangaroo rat. This sort of provender had been 
secured from a near-by meat-baited steel trap. From this incident 
we conclude that this species of squirrel is not altogether vegetarian in 
its food preferences. 

Very little information is at hand regarding the food carried in the 
cheek-pouches of this rodent. A specimen taken at McKittrick, Kern 
County, on May 19, 1911, had 744 seeds of the alfilaria {Er odium 
cicutarium) in its cheek-pouches. No food stores of any kind were 
found in the few burrows excavated. 

The Nelson Antelope Squirrel is distributed unevenly. It occurs in 
abundance at only a few localities. At one of these favored localities, 
eight miles northeast of Bakersfield, squirrels of this species were found 
scattered over the low hills in little colonies of six or eight individuals 
(H. S. Swarth, MS). It is believed that there were certain small areas 
here that supported at least twenty-five of the squirrels to the acre. 
However, they were present to this extent on only a small per cent of 
the total acreage inhabited. At San Emigdio llanch ten squirrels 
represent the greatest number found on any one acre. At McKittrick 
the number per acre was thought to be not over five. Taking the entire 
range of the species into consideration, there is probably about one 
squirrel to every two acres. 

Our impression is that on the east side of the San Joaquin Valley 
the range of this squirrel is now being rapidly restricted by farming 
activities. In 1911, and again in 1918, no Antelope Squirrels whatever 
could be found in the vicinity of the type locality, Tipton, in Tulare 
County, where it was common in June, 1893 (Merriam, 1893, p. 129). 
The first Nelson Squirrel was noted in the 1911 search thirty miles 
south of Tipton. The gradual settling up of the country, and the 
cultivation of the kind of ground inhabited by this squirrel, has resulted 
in the crowding out of the species over much of the eastern part of its 
original range. It seems only a question of time when continued 
reclamation will gradually restrict and eventually exterminate this 
species over the arable portions of the San Joaquin Valley. 

The Nelson Antelope Ground Squirrel is at the present time of little 
or no economic importance. It inhabits barren situations, apart from 
cultivated land. Our opinion is that this squirrel is not likely ever 
to become a pest. 



LOS BAi^OS ANTELOPE GROUND SQUIRREL. 
Ammospermophilus nelson! ampins Taylor. 



other names. — Nelson Ground Squirrel, part ; Antelope Chipmunk, part ; Atnmo- 
S2)e7'mophihis nclsoni, part. 

110 



THE GROUND SQUIRRELS OF CALIFORNIA. 703 

Field characters. — Exactly the same as for the Nelson Antelope Ground Squirrel. 

Description. — General coloration in all pelages exactly as in nelsoni proper, but 
clay color of upper surface a trifle paler, more buffy, and white side-stripes less dis- 
tinct. Size somewhat greater, especially as regards ears. 

Measurements. — Average and extreme measurements, in millimeters, of twenty 
full-grown specimens from twenty miles south of Los Baiios, in western Fresno 
County, are as follows: Ten males: total length, 246 (234-253) ; tail vertebrae, 73 
(G6-75) ; hind foot, 41 (40-43) ; ear from crown, 7.8 (7.0-9.0) ; greatest length of 
skull, 41.8 (41.0-42.7) ; zygomatic breadth, 24.8 (24.0-26.2) ; interorbital width, 
10.1 (9.4-10.4). Ten females: total length, 236 (230-243); tail vertebrae, 73 
(67-78) ; hind foot, 40 (37-43) ; ear from crown, 7.7 (6.5-9.0) ; greatest length of 
skull, 41.2 (39.8-42.0) ; zygomatic breadth, 24.3 (23.5-25.5) ; interorbital width, 10.0 
(9.2-10.3). 

Comparison with the measurements given for nelsoni will show that amplus is 
decidedly larger, with especially larger ear. 

Weight. — Only one record of adult weight is available, that of an old male, 186.3 
grams (6* ounces). 

Type locality. — Twenty miles south of Los Banos, Merced County [really near 
mouth of Little Panoche Creek in Fresno County], California (Taylor, 1916, p. 15). 

Distribution. — Known as yet only from a limited section of the floor of the San 
Joaquin Valley within 35 miles south of Los Bafios, in southwestern Merced County 
and northwestern Fresno County. Life-zone, Lower Sonoran. 

Specimens examined. — A total of 34 from the following localities in California. 
Merced County : Sweeney's ranch in hills "22 miles south of Los Baijos," 2. Fresno 
County : mouth of Little Panoche Creek, 18 or 20 miles south of Los Banos, 29 ; 
Hayes Station, B. M. 502, on Panoche Creek, 19 miles southwest of Mendota, 2 ; one 
mile east of Mendota, 1. 

The Los Baiios Antelope Ground Squirrel very closely resembles the 
Nelson Squirrel, and is doubtless practically identical with that form 
in general habits and locality preferences. More thorough exploration 
will probably show that the distribution of the two is continuous, in 
other words that the Los Baiios race has resulted from a northward 
extension of the ancestral stock which has allowed the acquisition of 
the slight differences of greater size and paler tone of coloration which 
characterize amplus. 

Along the western rim of the San Joaquin Valley south of Los Banos 
this subspecies is common locally. The type series was taken by R. H. 
Beck June 20, 1912, near the mouth of Little Panoche Creek, where the 
animals were found occupying holes on common territory with Cali- 
fornia Ground Squirrels. In one instance a ''chipmunk" was shot at 
the same hole with a "ground squirrel." 

Near the point where Panoche Creek breaks out of the liills, a few 
miles farther south, the last of June, 1918, museum collectors found a 
few Antelope Squirrels along roads between barley fields. The cheek- 
pouches of the two shot at the edge of such a field were full of barley 
grains. The breeding season on both the above dates was long passed ; 
young were nearly or quite full-grown. Remains of Ammospermophilus 
were found about the mouth of the burrow of a kit fox, evidence of 
the identity of one kind of enemy. 

The sort of country inhabited by this Ground Squirrel is arid and as 
yet to but a small extent under cultivation. Water is not available for 
extensive irrigation. The economic status already set forth for the 
Nelson Squirrel probably also holds for the Los Bafios race. 



704 THE MONTHLY BULLETIN. 

SUMMARY OF POINTS OF SPECIAL IMPORTANCE FROM 
THE STANDPOINT OF GROUND SQUIRREL CONTROL. 



From the foregoing account of the natural history of the ground 
squirrels of California the following facts and inferences stand out as 
seemingly of special importance in connection with the determination 
and application of methods of ground squirrel control. 

1. Of the eighteen kinds of ground squirrels occurring within the 
limits of the state, there appear to be only four meriting any particular 
consideration from an economic standpoint. These four are the Cali- 
fornia (or Beechey), the Oregon, the Fisher and the Douglas ground 
squirrels, here named in the estimated order of importance (see fig. 30). 
All the other fourteen kinds are, for the present at least, negligible, in 
most of the cases because they inhabit areas not cultivated by man. 

2. The Oregon Ground Squirrel is less than half the size of a ''dig- 
ger" squirrel, but it is ordinarily present in much greater numbers 
per given area within its range (most of Siskiyou, Modoc and Lassen 
counties) than is any one of the "digger" squirrels in its range. The 
Oregon inhabits open grass lands and hence comes into sharp competition 
with cattle interests. 

3. The Oregon Ground Squirrel is more of a grass eater than a seed 
or grain eater, and the most successful method of poisoning should 
involve the selection of an appropriate bait accordingly. It does not 
store up food to the extent that the "digger" squirrels do. The Oregon 
Ground Squirrel, more than any of the "digger" category, is subject 
to a sharply defined period of hibernation, and this involves all the 
individuals, of whatever age. 

4. The California Ground Squirrel is our species of greatest aggregate 
numbers and is the one which is most widely distributed over the 
cultivated parts of the state. Its close relatives, the Fisher and Douglas 
ground squirrels, are known along with the California as "digger" 
squirrels ; regarding most of the following considerations the three may 
be classed together. 

5. Because of relatively large size the individuals of the "digger" 
category are able to inflict serious loss. Adults average 1| to 1^ pounds 
in weight, and are easily able to consume -^ ounce of dry grain or 2 
ounces of green forage at a meal. 

6. On open range and pasture lands these squirrels feed largely on 
alfilaria and bur clover, two of the most valuable forage plants in the 
state. The squirrels are then serious competitors for subsistence against 
the flocks and herds upon which man depends for his own support. 
On cultivated ground these squirrels feed upon or destroy in other 
ways grain and fruit crops to a very large extent where present even 
in numbers not above those reached on wild land. The tendency seems 
to be to increase to extraordinary numbers on cultivated lands unless 
effectively cheeked by man. This is due both to improvements of food 
conditions from the standpoint of the squirrel, and to removal of its 
natural enemies by man either purposefully or thoughtlessly. 



112 , 



TPIE GROUND SQUIRRELS OF CALIFORNIA. 705 

7. The food preferences of ground squirrels are strongly in evidence 
and vary from species to species, and sometimes within the same species, 
from place to place and season to season. It is common testimony of 
those who have practical experience in poisoning ground squirrels that 
the Douglas is much more easily handled than the California; in other 
words, the former takes the strychnine-coated barley more readily. It 
is obvious that the success of any method of control l3y the use of poison 
must depend importantly on the nature of the bait employed. The fact 
that in some places the California Ground Squirrel has been found to 
pass up barley altogether for the seeds of bur clover suggests a likely 
way of improving poisoning methods locally. 

8. In the ' ' digger ' ' category of ground squirrels there is evidence that 
a greater or less proportion of the population hibernates each winter. 
In the Douglas this feature of the annual activity of the animal is 
clearly evident, in that the majority, or at the higher altitudes all, of 
the individuals disappear for weeks or months together during the 
winter season. In the case of the California Ground Squirrel, however, 
numerous individuals are to be seen aboveground in the lower country 
in favorable weather at any time during the winter. But evidence at 
hand goes to show that these active individuals are chiefly young of the 
year and that most of the older scpirrels are then lying dormant below- 
ground, in some extreme cases for as long a period as from August to 
February. During this interval, therefore, any method of poisoning, 
and probably also of gassing, will obviously be ineffective upon a portion 
of the population, and this portion which escapes will reappear at the 
beginning of the next breeding season to reinfest the area concerned. 

9. Some obstacles to the success of control by the method of gassing 
arise through the unequal extent and irregular course of the burrows 
of the squirrels. It was found that although the volumetric content 
of the burrows of the California Ground Squirrel excavated averaged 
5.2 cubic feet, in one case an extreme of 17.8 cubic feet was reached. 
This obtained in one of the ''colonial" types of burrows in which several 
establishments supposed to have been originally separate had come to 
be intercommunicating. It was found that the usual dosage was ineffec- 
tual in this case. There is no definite way of distinguishing such 
"colonial" burrows, from surface appearances alone. Then, again, in 
some burrows there is an abrupt rise in the underground course of the 
burrow, which prevents the onward flow of a gas heavier than air, such 
as carbon bisulphid, and the scpiirrel is not overtaken. In either of the 
above circumstances Ave find a reason for the partial failure of extensive 
gassing campaigns with current methods. 

10. Ground squirrels reproduce rapidly. In the California the 
average number of young in a litter is 7.2, with 4 and 11 as extremes. 
There is but one litter reared each year, and the young begin to appear 
aboveground about the first of May. The sexes are equally divided in 
a given population, and it is believed that each female breeds the first 
season of her life, that is, when she is slightly less than a year old, and 
that she has an ''expectation" of rearing four more litters in case she 
lives to die of old age. Thus a population of 10 per acre in March may 
be expected to increase to 50 per acre by the last of May. Postponement 
of attention by the farmer is a losing proposition. A stitch in time 
actually saves nine. 

8— 43C0-7 113 



706 



THE MONTHLY BULLETIN. 



11. The general habits of ground squirrels are such that they were 
able to hold their oAvn in the face of a host of natural enemies which 
habitually preyed upon them before the white man's advent. The 
squirrels are eminently successful in the battle for existence. They 
inevitably prosper when any natural cheek is removed. 

12. The recuperative powers of ground squirrels are great. It is 
shown that if the population of one square mile (if estimated at 640 
as in the ease of the California Ground Squirrel) were subjected to two 
successive control campaigns, each of 90 per cent effectiveness, there 
would still remain six squirrels; these three pairs of squirrels would 
theoretically at the end of the third breeding season give rise to the full 
normal population of 640, Avith a good margin for natural death. It 
would seem that, if absolute extermination prove not possible over any 
large area, eternal vigilance must be exercised to prevent the quick 
return of the squirrel population to the danger point. The squirrels 
must be looked after like weeds, which have to be dealt with year 
after year. 

13. Ground squirrels breed upon uncultivated or Avaste land, from 
which they invade the cultivated fields Avithin reach as well as such other 
lands as are not already fully populated. There is progressive emigra- 
tion of a certain portion of the squirrel population each year, in August 
and September, involving chiefly or entirely the young of the year just 
coming to maturity. By a process of gradual infiltration, land once 
thoroughly rid of squirrels may thus be reinfested from more or less 
distant areas of dissemination. Lands successfully poisoned in the 
spring may be found repopulated the folloAving fall from some adjoining 
territory. 

14. Since the squirrels if not interfered with by man are stopped in 
their emigrations only at some natural barrier, it seems clear that control 
campaigns should not be limited by political or civil boundaries such 
as state, county, district or property lines. Rather should natural 




• Fig. 30. Diagram showing estimated relative importance, as regards economic status, 
of the different species of ground squirrels in California, a, California (Beechey) 
Ground Squirrel ; h, Oregon Ground Squirrel ; c, Fisher Ground Squirrel ; d. Douglas 
Ground Squirrel ; e, all other species of ground squirrels in the state put together. 
The estimated ratios are, respectively, 10—5-4-3-1. 

114 



THE GROUND SQUIRRELS OP CALIFORNIA. 707 

barriers be hewn to, such as those of climate, seaeoasts, rivers, brush 
lands and deserts. The forest ranger in anticipating the sweep of a 
potential fire, or in combating any actual fire, outlines his campaign 
irrespective of any but those lines ■which will naturally aid most in 
stopping the spread of the conflagration. 

15. If "drive weeks" be advocated, as a popular measure to secure 
control locally, the time of the year selected should be fixed in accord- 
ance with the optimum chances for success, on the grounds of avidity 
of the squirrels for kinds of bait available, minimum natural population 
(previously to the time of appearance of the young), ancl probable 
weather conditions. 

16. The above general remarks must not be construed as in any degree 
intended to discourage the continued energetic application of the best 
methods of ground squirrel control now in use. But it is hoped the 
facts and inferences set forth will convince the reader that the problem 
is not a simple one, and cannot be solved by casual, half-hearted meas- 
ures. It is believed that great improvement can be secured both in 
devising of method and in mode of application. 



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1917. Control of the California Ground Squirrel. Univ. Calif. Agric. Exper. 

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1908, The Biota of the San Bernardino Mountains. Univ. Calif. Publ. Zool., 
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1913. A Distributional List of the Mammals of California. Proc. Calif. Acad. 

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1914. An Account of the Mammals and Birds of the Lower Colorado Valley with 

Especial Reference to the Distributional Problems Presented. Univ. 
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1918. Six new Mammals from the Mohave Desert and Inyo Regions of California. 

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708 



THE MONTHLY BULLETIN. 



(jrinnell, J., and Swarth, H. S. 

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1907. Mammals of the Mexican Boundary of the United States. U. S. Nat. 
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1918. Smaller Mammals of North America. Nat. Geog. Mag., vol. 33, pp. 371- 

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Richardson, J. 

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116 



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